Though the 4vyb for 1 was expected to be valid for 150,000 coins, it seems to have collected 92000 POB. Not sure what does it mean.

Sending POB to the @x-1pob-4vyb account with the word 'market' in the memo means "I want to exchange these POB tokens for VYB tokens at this exchange rate or the next best available exchange rate(s)." A lot of folks have been using that approach.