Adding a number to a 'set value' in SC appends it rather than adding to its value

Wappler: 4.6.4
OS: MacOS
Server Model: PHP

I have some ‘set value’ actions in my Server Connect and am trying to increment one but it’s appending it instead. I have it set as a number and not text and also tried surrounding it with brackets but this is happening:

If var = 12, var + 1 should = 13 but it’s setting it to 121.

I’ve spent ages trying to get it to work but without any success. I’ve tried editing the SC in code view and formatting it there, too.