Correct. When wagering the bonus, there are special rules regarding maximum bets and available games. During bonus wagering, bonus bets should not exceed 5 EUR, 5 USD, 7.5 CAD, 7.5 AUD, 50 NOK, 25 PLN, 7.5 NZD, 625 JPY, 2,500 KZT, 0.0001 BTC, 0.01 BHC, 0.0014 ETH, 0.045 LTC, 35 DOG, and 5 USDT.
Some games (including all jackpot games) are unavailable for bonus wagering. The jackpot category is closed if a player has active bonuses. But there are also slots that open to playing with bonuses but don’t provide wagering. When you open such a slot (unavailable for bonus wagering), you will see a notification “Bonus wagering is not available. Max bet with bonus is XX EUR”. Where XX — is the amount of max bet using bonuses.
During the wagering, you can’t buy bonus rounds and can’t double your bets.