How I make my slash effects - gmod pac3 tutorial

first tutorial :00 1-1 clamp expression: 1-clamp(timeex()*10,0,1) idk what the 0 in the middle does download this example: https://www.dropbox.com/scl/fi/q2smp8i3mqrw8zlg6zmqn/slash-example.txt?rlkey=2vlkbi7hv0tqosec40rqg49su&st=wz9ki4r3&dl=0