You can understand what you will get with a deposit 5 play with 40 casino bonus by reading the terms and conditions: You can either get 40 EUR or 40 free spins, depends on the bonus itself.
These are also advantageous bonuses, as you can win much more with your free spins. For example, a deposit 10 get 60 bonus can give you 60 free spins to use on slot machines, in exchange for depositing 10 EUR. However, sometimes the “Y” shows the number of free spins you will get, instead of the cash amount. This means it is actually a match bonus with a 300% rate. For example, a deposit 10 get 30 bonus will give you 30 EUR, in exchange for making a 10 EUR deposit.
Usually, the “Y” is a number that shows the cash amount. “Deposit X get Y” bonuses are simple: The “X” shows how much you need to deposit and the “Y” shows what you will get.