What does "Okay. So, let’s say at seven." mean in English for Spanish?

In English for Spanish, "Okay. So, let’s say at seven." means:

Así que, digamos que a las siete.

Listen to "Okay. So, let’s say at seven.": (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 4, Level 3, Scene 5