How do I correctly add and subtract to a variable

I want one instance to add and another to subtract, but it is not working

The simplest way would be to add a “Number” behavior node. It has a “+” input, and any value you send to that input will get added. For instance, to add 5 to the number, just send a 5 to that input. To subtract 5, send a -5 to that input instead.

Thank you! I thought I had to use expressions.

Either work though