EX-1 & XPro-1 Exposure Dial

A long time user of the S3 Pro here and my technique is old-school fully manual so forgive me if this question seems odd.

I notice the exposure dial goes from 250th/sec to 500th/sec. Does this mean no 350th/sec or similar is possible? Or is it such with these new cams that fine tuning the ISO can give you the aperture setting you want with what would normally be at around 350th/sec but using 500th/sec?

I have a feeling there's going to be a fair learning curve ahead for me moving from S3 Pro to either the EX-1 or XPro-1.

Cheers