increment Commandincrement <target> [by <number>]
The increment command adds to an existing variable, property, or attribute. It defaults to adding the value 1, but this can be changed using the by modifier. If the target variable is null, then it is assumed to be 0, and then incremented by the specified amount. The increment command is the opposite of the decrement command command.
If you target a string variable, then increment uses += to add the string to the end of the target variable.
set counter to 5
increment counter by 2 -- counter is now 7
increment newVariable -- newVariable is defaulted to zero, then incremented to 1