VAT Exclusion Calculation--- when to use it?

So the calculation for "VAT exclusion" is (Gross Amount / 1 + VAT%) - Gross Amount
But when do you actually use this, what does it actually tell us?
Thanks.
But when do you actually use this, what does it actually tell us?
Thanks.
Answers
GROSS AMOUNT - (Gross Amount / 1 + VAT%)