Q: Is this how I calculate expense overages?

Hi. Bit of context. I have a budgeting workbook that tracks money in and money out. On the summary page, I have income, savings, and expenses. I calculate over/under budget by taking Income - Savings - Expenses. I calculate how much cash I have left over by taking Income - Expenses. I calculate how much liquid cash I have by taking Income - Expenses - Roth IRA contributions (a Savings account).

Is it correct to calculate the over/under for expenses by taking leftover cash minus my savings' goal? In example, I have leftover cash of $2,876.71. My savings goal is 20% of my total income which comes out to $4,377.46. If I take $2,876.71 - $4,377.46, is that ($1,500.75) how much I've overspent in expenses? (I put 26% into my Savings accounts this year but had a large car repair/maintenance expense that dipped into it.) I can't seem to wrap my head around it and would love some confirmation.

(I don't need to calculate the over/under for expenses between my projected budget and my actual expenses.)