I was frustrated by that because i kept trying to buy 10 at once and they never had 10 at the same time.. i did that all day until i had the bright idea to  buy in smaller amounts.  I was able to buy my 10 over the course of about 10-15 minutes by buying 1 or 2 at a time.. just hope my bank doesn't freeze my account because it looks so suspicious.

edit:  coinbase's daily max limit is a rolling limit, not a specific point in time where the limit is cleared.  the 6am time they give in the notice is just a suggestion where more are most likely to be available, but you can get them any time if you only get 1 or 2