How are multiple credit memos applied?

We have a situation in 11.5.10.2 where credit memos are not being applied chronologically.  In other words, credit memos that are newer are being applied to invoices before an older credit memo.  This does not seem like correct behavior.  These  invoices and credit memos are being brought in through the open interface and are not being handled manually.  We would expect the oldest credit memo to be applied first. 

Thanks, Susan