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Unless you wait a bit, the additions and deletions won't be reflected.
Literal
Time [object-を] not-placing-[conditional-と] additions/deletions [subject-が] are-not-reflected.
A technical instruction about system behavior. 時間をおく ('put time / leave an interval') is idiomatic for 'wait a bit.' ~ないと is the casual conditional 'if not / unless' — short for ~ないといけない but here just stating what happens without the wait. 反映される is the passive of 反映する ('to reflect'), used naturally in tech contexts for data updates. 追加・削除 uses the nakaguro (・) to join two related operations.