Field help (AWPDATMAXS) 

This field contains the date on which the Workflow shall have been signed. It is equal to the triggering date if no signature process has been implemented, or if no deadline has been defined.

In fact, when the Workflow event expects a signature :

When a reminder of this type is made :

If these batch rules are not used and if no other rule has been defined to change these fields, the number of reminders remains equal to 0 and the reminder date remains empty, because no other standard Workflow process can modify this value.