align the calculation of unit with stock in line data create calculation

src/app/api/po/index.ts

@@ -60,6 +60,9 @@ export interface StockUomForPoLine {
   stockRatioD: number;
   purchaseRatioN: number;
   purchaseRatioD: number;
+  sourceRatioN?: number | null;
+  sourceRatioD?: number | null;
+  stockQtyInteger?: boolean | null;
 }
 
 // DEPRECIATED

src/components/PoDetail/PoDetailRow.tsx

@@ -117,6 +117,7 @@ export const PoDetailRow = memo(function PoDetailRow({
         orderQty,
         Number(row.stockUom?.stockQty ?? 0),
         acceptedQty,
+        row.stockUom,
       );
 
       const doSubmit = () => {
@@ -211,6 +212,7 @@ export const PoDetailRow = memo(function PoDetailRow({
     Number(row.qty ?? 0),
     Number(row.stockUom?.stockQty ?? 0),
     enteredBatchQty,
+    row.stockUom,
   );
   const convertedStockQtyWithUnit = formatQtyWithStockUom(
     convertedStockQty,

src/components/PoDetail/stockQtyRound.ts

@@ -7,16 +7,95 @@ export type StockQtyRoundChoice = {
   after: number;
 };
 
-/** FP-MTMS Version Checklist | Functions Ref. No. 56 | v1.0.4 | 2026-09-10 */
+/** Keep in sync with ItemUomService.isIntegerCountStockUom */
+const INTEGER_COUNT_UNIT_TOKENS = new Set([
+  "包",
+  "箱",
+  "件",
+  "個",
+  "PCS",
+  "PC",
+  "CTN",
+  "EA",
+  "PK",
+  "PKT",
+  "BOX",
+]);
+
+export type PoStockQtyConvertHint = {
+  sourceRatioN?: number | null;
+  sourceRatioD?: number | null;
+  stockRatioN?: number | null;
+  stockRatioD?: number | null;
+  purchaseRatioN?: number | null;
+  purchaseRatioD?: number | null;
+  stockUomCode?: string | null;
+  stockUomShortDesc?: string | null;
+  stockQtyInteger?: boolean | null;
+};
+
+function toRatio(value: number | null | undefined): number | null {
+  const n = Number(value);
+  if (!Number.isFinite(n) || n === 0) return null;
+  return n;
+}
+
+function stockQtyMustBeInteger(hint?: PoStockQtyConvertHint): boolean {
+  if (hint?.stockQtyInteger === true) return true;
+  if (hint?.stockQtyInteger === false) return false;
+  const code = hint?.stockUomCode?.trim() ?? "";
+  if (code.toUpperCase().startsWith("PCS/CTN")) return true;
+  const short = hint?.stockUomShortDesc?.trim() ?? "";
+  return INTEGER_COUNT_UNIT_TOKENS.has(short) || INTEGER_COUNT_UNIT_TOKENS.has(code.toUpperCase());
+}
+
+/** Java BigDecimal HALF_UP for non-negative qty. */
+function roundHalfUp(value: number, scale: number): number {
+  const factor = 10 ** scale;
+  return Math.round(value * factor) / factor;
+}
+
+function finalizePoStockQty(raw: number, hint?: PoStockQtyConvertHint): number {
+  if (!Number.isFinite(raw)) return 0;
+  return stockQtyMustBeInteger(hint) ? roundHalfUp(raw, 0) : roundHalfUp(raw, 2);
+}
+
+/**
+ * Same ratio path as backend convertQtyToStockQtyPrecise:
+ * base = qty * sourceRatioN / sourceRatioD
+ * stock = base * stockRatioD / stockRatioN
+ */
+function convertPoBatchToStockQty(
+  batchM18Qty: number,
+  hint?: PoStockQtyConvertHint,
+): number | null {
+  if (!hint || !Number.isFinite(batchM18Qty)) return null;
+  const sourceN = toRatio(hint.sourceRatioN) ?? toRatio(hint.purchaseRatioN);
+  const sourceD = toRatio(hint.sourceRatioD) ?? toRatio(hint.purchaseRatioD);
+  const stockN = toRatio(hint.stockRatioN);
+  const stockD = toRatio(hint.stockRatioD);
+  if (sourceN == null || sourceD == null || stockN == null || stockD == null) return null;
+  const baseQty = (batchM18Qty * sourceN) / sourceD;
+  const stockQty = (baseQty * stockD) / stockN;
+  return finalizePoStockQty(stockQty, hint);
+}
+
+/**
+ * Preview converted stock qty for a 來貨數 batch.
+ * Matches create-stock-in: ratio convert, then integer HALF_UP for 包/箱/PCS, else 2 decimals.
+ */
 export function previewPoBatchStockQty(
   orderM18Qty: number,
   orderStockQty: number,
   batchM18Qty: number,
+  hint?: PoStockQtyConvertHint,
 ): number {
+  const fromRatios = convertPoBatchToStockQty(batchM18Qty, hint);
+  if (fromRatios != null) return fromRatios;
   if (!Number.isFinite(orderM18Qty) || orderM18Qty === 0) {
-    return Number(batchM18Qty.toFixed(2));
+    return finalizePoStockQty(batchM18Qty, hint);
   }
-  return Number(((batchM18Qty * orderStockQty) / orderM18Qty).toFixed(2));
+  return finalizePoStockQty((batchM18Qty * orderStockQty) / orderM18Qty, hint);
 }
 
 export function isNotIntegerQty(qty: number): boolean {