I havent got the advance scheduler on Mango .
Do i have to dowload that module especially ? (it should have been with all the package 3.6 ? No ?
Yes, I believe it should have been in the bundle download on the store if that's what you mean, yes. You can install it from the modules page by checking for updates, it would appear in the "available for installation section". It's not clear if you're fully up to date from the images you posted.
It does appear to be missing from the bundle currently, so I'll look into that and thanks for bringing it to our attention.
I tried to change the step option to bar without success.
Assuming you are fully up to date, does this happen every time? As I said, I was not able to replicate. Can you give more detailed instructions on how to cause the issue?