Passing through PVG Two Times

I am travelling for two weeks round-trip to Shanghai from the USA. During this time, I plan on visiting Tokyo for a week. Can I get a 144 TWOV permit for the first 6 days I am in Shanghai, then travel to Japan, then back to Shanghai before flying back to the USA?

Also, if I plan on staying a few more nights in Shanghai before returning to the USA, is that allowed under another 144 TWOV permit? Thank you!