Diagnosis
You have entered more than one size and a variable-size part unitwithout dimension.
If no formula is entered, the sizes entered are multiplied with eachother. If a variable-size part unit is without dimension, no properresult is produced.
Example:
Var-size unit PC (without dimension)
PC * PC --> ?
In contrast:
Var-size unit M (length)
M * M --> QM (area)

Procedure
Check your entries.
Correct variable-size part unit or size as appropriate or enter aformula for calculating the variable-size part quantity.