You create a random value per particle, in a range of let’s say 0…1. Now what the value to time setup gives you, is basically the position in the animation of a certain node, for each input value. It’s exactly that animation that you can control in the curve editor to get biases, etc. So the setup is - random-valuetotime-float, with the time output of the VTT linked to the time input of the float. then you tweak the float’s curve, and probably multiply by a max value its output, and there you go. Non-linear animation is a bit of a brainbender, but it’s explained in my DVD, so you might wanna check that out 