Definition - What does Pro Tanto mean?
Pro-tanto means as far as it can go or for as much as it is able to. The term references a payment made on a larger debt that represents only part of the whole. This term is also used within eminent domain and compulsory purchase orders.
Justipedia explains Pro Tanto
A judge can also order that payment are made for a set amount of time pro tanto; meaning that the payments will be decreed to continue for the length of time that is stated at the outset.