Probably not over 1.05 is 'safe', but imo it's useless since you're probably just winning a few ms. You shouldn't use this on a server that has a decent anticheat, for ex. badlion, just don't.
What I meant by ms is for example you will take a little bit less time eating a gapple (or any other thing). (you will probably not even notice the difference) but imagine eating a gapple takes 2.50 seconds. With timer enabled (in this case the value is set to 1.05) the gapple eating time will now be reduced maybe to 2.15 seconds (I'm just guessing random numbers, I hope you get the point). Anyway I'd suggest you not to use this module since anticheats do detect it.So all it does is make your Ms Better or makes it so you have a advantage?