Estimated after merge coverage is more as compared to after merge

For one of my projects when merge build is triggered estimated after merge coverage is around 63.1 % and after it is merged it fails quality gate as coverage is 57% which is less than 60% required criteria , What could be the probable reasons for this as i’m unable to figure out the issue .

Hi,

Were multiple PRs merged at or around the same time? Quality gate criteria on coverage and duplications aren’t enforced when there are fewer than 20 new lines. So if other, small PRs were merged about the same time, that could explain this behavior.

 
HTH,
Ann