The reason why the Account set in the Expense Allocation Schedule > Source tab > Credit Account field results to a Debit in the Allocation Journal Entry.
The Account set in the Expense Allocation Schedule > Source tab > Credit Account field is expected to be the Credit in the Allocation Journal Entry, as the word itself is 'Credit Account'.
But this is just an offsetting account, and would not automatically be a Credit in the Allocation Journal Entry.
The usual expectation is that the Account set in the Credit Account field will result to a Credit in the Allocation Journal Entry as Expenses are in the normal balance of Debit, so it will process an offset. Note: If the total amount of the Source Account (usually an expense) of a certain period results in a Debit, then this will be the normal behavior.
Sometimes this is not the case because the total amount of the Source Account (usually an expense) of a certain period results in a Credit, then the Account set in the Credit Account field will result to a Debit in the Allocation Journal Entry. This is the behavior because it is offsetting the amount.