Here you can build a register of fixed dimensions that you use in your project, eg windows, interior doors.
You can then use these in the formulas under Number in your calculation.
For example, V-id90, id90 then refers to the dimensions of an inner door that is 90cm. 2.1 * 0.9
Press add and then fill in the fields
Name - the name you give is what you will use in the number of columns.
Value - a mathematical formula where you can calculate what you are looking for (see picture), it can also be a finished calculated number.