What they mean is that Google takes the money from your account ASAP, but we (the people you are paying) don't actually get it for a little while longer. So from your end, it looks like you paid, but in reality the money is 'in transit.' This is normal. The money is removed from your bank account ASAP, but there's a small wait time to ensure there isn't any money laundering going on.
(Confession: I worked in banking for a long time).