The phrase "allowable amount" refers to the maximum or acceptable quantity or limit that is allowed or permitted. It indicates the amount that is within the rules or guidelines set. Full definition
He used the maximum allowable amount of margin (slightly over 50 %). (valuewalk.com)
The proposed rules also invite input on the maximum allowable amount of commercial space for these properties, which is set at 50 percent in the law. (realtormag.realtor.org)
Specifically, that means allowable amounts for such things as medical expenses, moving expenses, child care costs and charitable donations. (moneysense.ca)