Blue Iris not deleting clips that happen the last couple weeks of each month

[questioning]

I have Blue Iris set to delete clips when the storage reaches a certain size. This is weird, but it seems Blue Iris is not properly deleting clips from about the last two weeks of each month. When I go back and look at the clips, each of the past several months has clips from the last couple weeks of September, August, July, etc. Any idea why it would be not deleting those clips?

This is Blue Iris version 4.8.6.3.