Where low house edge games are permitted while a bonus is being cleared, the contribution percentage will almost always be altered. That means that while you may wager a thousand dollars on a particular game, the casino will apply a percentage to your wager total to determine how much will count towards the wagering requirements.
Effectively, this means that the player must bet a lot more on those games than they would have to bet on a game that contributed 100% to the rollover. The percentages are different from game to game, and from casino to casino.
While a bonus is in play, that is, while you have received a bonus but have not yet wagered a total amount greater than the amount calculated by the terms of that bonus, you will be restricted in what games you are allowed to play, and in many cases, you will also be restricted in the amount that you can bet on each spin, hand or bet.
It is very important that you know what restrictions apply to your bonus, and that you stay within those rules.
As a standard procedure online casinos will review all your play once you submit a cashout request. Any breaches of the rules will be easily spotted at that point, and they will simply remove the bonus, and possibly any associated winnings, from your account. You cannot really win in an argument with them if you can clearly be shown to have broken the rules, so it really is better to stick to the terms.
Another tricky rule buried deep in the terms is the maximum bet or maximum wager rule. Essentially, the casino wants you to play as much as possible while you are clearing a bonus. it is not jsut about the amount of the wagering requirement, it is the number of bets that it takes to complete that requirement.
If you were allowed to complete the requirements in one go, then presumably about half of the players would lose and the other half would win. That would cost the casinos a lot of money.
Instead they want you to make as many wagers as possible. As every gambler knows, the more you play the more likely it is that the house edge will catch up with you. Well, the casinos know this too, and make sure that you have to make a lot of bets in order to reach the required wagering amount.
To do this they will impose maximum bet sizes on your play. The sizes that apply to you should be in the term sof the offer. The maximum size is often calculated per spin, round or deal, and not by the individual bet.
For example, if the max. that applies is $5.00 then you cannot bet $5.00 on every number of the Roulette wheel for each spin. No, instead the most you can bet across those numbers on one spin must total $5.00 or less, in this example.
The size may be stated in a fixed dollar amount, or may be a percentage of the total bonus you have got to play.
Also, trying to cover too many bets on games suxch as roulette may cause you to fall foul of other general bonus abuse terms, so do be careful when playing games where there are multiple betting options availabel on each round of the game, such as roulette.