Card counting systems aren't necessarily correct or incorrect. Hi-Lo and Red7 are both perfectly valid systems. The main difference is that Hi-Lo is "balanced" meaning that there are an equal number of positive and negative cards (you start at 0 and end at 0). Whereas Red7 is unbalanced (hence counting half the 7s). With Hi-Lo, you need to divide the running count by the remaining decks to get the True Count to know how much to bet. With Red7, there's no division, you just bet according to the running count.
And with that out of the way, ANY card counting system is 100% useless in almost all on-line casinos because the cards are shuffled after every hand. And I don't know to which casino you're referring, but you should know (if you don't already) that the bonus is "sticky", meaning you can never withdraw the $800.
that makes much more senses to me now.The online casinos i am mainly talking about are the live dealer ones where you can see everything happening just as if you were really there.Most of these live dealer casinos use shoes of about 8 decks and only get shuffled at the end of the 8 decks then they use another 8 decks and just keep rotating it at the end of each shoe.However i didn't realise about the "sticky" bit so thanks, ill take that into consideration