update

src/main/java/com/ffii/tsms/modules/report/service/ReportService.kt

@@ -661,7 +661,7 @@ open class ReportService(
 
         val sumUInvoiceCell = row.createCell(14)
         sumUInvoiceCell.apply {
-            cellFormula = "SUM(O15:O${rowNum})"
+            cellFormula = "=IF(H${rowNum}-N${rowNum}<0,0,H${rowNum}-N${rowNum})"
             cellStyle = boldFontCellStyle
             cellStyle.dataFormat = accountingStyle
         }