+ and - Help Please

Hi
Happy New Year everybody.
:p:

Can you please help me do the following action in the movie I send in the attachement below…

For the + button
it should just add “1” to the variable Percent on each press
Exp : first press = 1, sec. press =2, third Press 3 and so on

For the _ button
it should just remove “1” to the variable Percent on each press
Exp : first press = -1, sec. press =-2, third Press -3 and so on
but if Percent was already at 3 for example:
Exp : first press = 2, sec. press =1, third Press 0 and so on

Thank you