A spending worksheet says 60, while the recorded purchase says 72. The difference is 12, but the subtraction does not explain what happened. A useful review asks what the two numbers include.
Rebuild the planned amount
In an invented example, the plan allowed for six identical items at 10 each. The purchase was six items at 12 each. The quantity stayed the same; the price assumption changed.
If the purchase had instead been eight items at 9 each, the same actual total of 72 would have a different explanation. Keep the units visible before describing the difference.
Check the date boundary
A purchase planned for next month may have happened early. That does not make it free, but it changes how a one-month comparison should be read. Note the timing instead of moving entries merely to make a column look better.
Write an explanation, then a question
“Six items cost two more each than assumed” is a clear explanation of this fictional calculation. “Was the old price an estimate or a quoted price?” is a useful follow-up.
For real financial choices, verify the underlying records and your circumstances. This exercise only illustrates a way to read differences. Pair it with checking assumptions in financial examples so that the next plan rests on information you can identify.