In FMP help... "After the specified interval has passed, the next time the application is idle, run the script"...
so here is what i think is happening in FMP pseudo code...
install timer (script "a"; 10)
set var interval = 10
set variable interval = interval - 1
Exit Loop if interval = 0
Exit Loop if script can be executed
fire script "a"
What can cause delay in the second loop?