Wait for it to load and then press space if you want it to calculate the amount of clones you can have running with effects at the same time without making the FPS going below the minimum FPS :)
You can change the Minimum FPS from 3 to 30 :) The maximum FPS for Scratch is 30 I think, so that's why it's the maximum. 3 FPS is the minimum because if you have music on a project with lower than 3 FPS the music often sounds really weird.
The amount of clones is the amount of clones that will run.
You can use this to make your project adjust itself so that it doesn't lag that much :)
FPS = Frames Per Second
UPS = Updates Per Second (Updates Per sprite every Second)
UPS is the same as TPS; Ticks Per Second :)
The loading bar only guesses how long time it should be left :)