SLA for the re-open tickets is not working right

SLA for the re-open tickets is not working right

Dears,Could you help me in the below issue;-
if we have resolved ticket and before the ticket get closed by system the requester has re-open the ticket and the ticket become due even if the ticket have a few hours.
- second case if the ticket closed and the requester has re-open the ticket the new SLA is less than SLA that should given while re-open the ticket......could you help me to know the reason and the solution to fix this problem.
Thanks in advance

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