What does "You should add a tip." mean in English for Spanish?

In English for Spanish, "You should add a tip." means: (también: Deberías ....)

Debería añadir una propina.

Listen to "You should add a tip.": (If you have an HTML5 enabled browser, you can listen to the native audio below)

This is a phrase that is used in the GamesForLanguage English for Spanish Language Game in the following scenes:

• English for Spanish 3, Level 3, Scene 3