Question regarding summing formulas

Hello,

I'm trying to create a column where a formula adds the numbers in several other columns.

Example

Variable_1 = 2

Variable_2 = 1

In the summed column, I'm selecting "formula" and typing

(Variable_1 + Variable_2)

Instead of getting "3", however, the field is displaying "21"

What am I doing wrong?

Thanks in advance!