Help please I'm new to this program!

Hello everyone,

I have used this program for cleaning internet history and so on.

I found this driver wipe and I selected free space and the last option there was some number 35 If im right it has been doing some stuff for 8 hours so far and when I opened my computer I had 2.54 gb left I used to have like 150 gb free space tell me is it normal and what does it help takeing all my space.

Can anyone explain what it's good for?

Thank you.