can anyone suggest on how to set unlimited approval limit for an authorized approver.

as per the the training guide page 26 in the below link it says "If you want this authorized approver to have limit approval, select the currency and the amount. If they are to have unlimited approval, set to no approval limit currency, and leave the approval limit amount blank."

Concur Expense: Workflow – Authorized Approvers Setup Guide (concurtraining.com)

however, we cannot save with out selecting any currency and amount limit in authorized approvers section of workflow. and there is one topic says we need to enter NULL and not clear guide on where and how to do it. (amount field cannot be entered with text NULL"