Print that string out to see what it really is. Because it its representation of number it should be translated to float.
You are also spamming play matine on event tick, you need do once there and the reset it when matinee is done with playing.
Split problem into 2 basic problems, i have strange feeling that you are fighting 2 “kicking horse contests” at once: wrong string and wrong matinee setup.
To test matinee: make some keyboard event, and when pressed play matinee, then add that do once and reset when matinee finished.
For string: print out what string really looks like.