Whilst bonus wagering, not all games contribute equally to the wagering requirements. This is enforced to counteract the relatively high payout potential certain games have over others, i.e. table games over slots.
So, whereas slots will contribute the full £1 for every £1 wagered, roulette may be weighted down at something like 20%. Now, just £0.20 will be counted for every £1 bet placed.
We explain more about this term in our game weighting guide.