diff --git a/src/State/EmployeeLeaveSummaryProvider.php b/src/State/EmployeeLeaveSummaryProvider.php
index aef813f..5ee8c76 100644
--- a/src/State/EmployeeLeaveSummaryProvider.php
+++ b/src/State/EmployeeLeaveSummaryProvider.php
@@ -193,6 +193,13 @@ final readonly class EmployeeLeaveSummaryProvider implements ProviderInterface
                 $leavePolicy['countOnlyCp'],
                 $leavePolicy['splitSaturdays']
             );
+
+            // Bootstrap support: if the opening balance has pre-filled taken days
+            // (e.g. manual data entry for production bootstrap), add them as an offset.
+            if (null !== $openingBalance) {
+                $takenDays += $openingBalance->getTakenDays();
+                $takenSaturdays += $openingBalance->getTakenSaturdays();
+            }
             if (LeaveRuleCode::CDI_CDD_NON_FORFAIT->value === $leavePolicy['ruleCode']) {
                 $availableAcquired  = max(0.0, $carryDays);
                 $takenFromAcquired  = min($availableAcquired, $takenDays);