The English translation is odd. It should be either "You should leave the tip..." or "Leave the tip...".
A mon niveau actuel, je pencherais pour le conseil ou pour l'impératif aussi.
I chose "leave the tip..." and it was accepted.
[PE] 1 n Tip, gratuity, service charge.
Put the tip on the table was NOT accepted, but seems less stilted than the preferred answer.
Dang, I typed "a" instead on "the" before the word "tip".