Admins can view the usage status and keep track of Updated Document usage at any time by going to Settings > Organization > Billing inside the app.
Updated Documents are counted as:
Merge: Number of input files x number of rows
Find and Replace: Number of input files
Merge from the Form View: Number of input files
Which options are counted?
When choosing 'Save updated documents as', only one option counts towards your usage limit. For example, you can toggle all of 'Word', 'Word with Tracked Changes', and 'PDF' on, and it will only be counted once towards your usage limit, not three times. Furthermore choosing to save redlines, saving editing instructions as excel files, or saving original documents also doesn't count towards the usage limit.