how to add a new value to the previous value in another table

[codename-12]

I have a table that has a condition where if there are the same items it will add the value and if there are none it will add a new row

so I created an action that uses input as a stored value variable

then i put this action on automation with operator "+"

in monitor says ok but the value didn't change

any tips for solve this issue? thank you in advance