Invoice Authorizer Assigning Rule - Absolute values?

I’ve come across a scenario for manual supplier invoice authorisation where an invoice is matched to a sub contract where retention applies and this has generated negative lines for the retention amounts. 

I’ve noticed that the amount on the posting seem to be absolute values, i.e. non-sign specific. 

For example, this rule will apply for all postings where the amounts are within -4999.99 and 4999.99 and I want to check if this is correct and it’s done by design?