Typing quickly or pasting the values in will allow the changes to be entered correctly. Having the 'Action' tab open (selected) while modifying the Schedule will allow confirmation that a change has/has not occurred to the email recorded under "Send Email [xx] Days before scheduled change"
This issue was addressed in TPAM 2.5.919. From the TPAM 2.5.919 Release Notes "Resolved Issues" section:
"Issues editing and saving the Send email X days before scheduled change to X setting on the Password Change Profile editor page.