The calculation is right. What can the person do with it?

A budget remainder needs to account for upcoming commitments.

Illustrative budget allocation on an aluminium tray. Seven graphite tokens of 100 euros represent 700 euros in upcoming bills; one lime token of 100 euros is unallocated. An 800-euro budget remainder may include commitments. Fictional data.

Say you have a €2,000 monthly budget and have spent €1,200. The assistant tells you there's €800 left. The subtraction is correct.

But suppose €700 in bills still needs to come out of that budget. Now only €100 is unallocated. And neither figure tells us the account balance or whether there are other commitments we can't see.

This is what bothers me about presenting a number without showing what went into it. The person may be trying to decide whether they can afford something. We give them a correct calculation that leaves out something important to that decision.

So I want to see which spending and upcoming bills were included, and have a way to correct them. If a bill is already paid, I should be able to say so. If an account is missing, show me. A label saying “estimate” won't explain any of that on its own.