Phrases Asking for Clarification

I'm not entirely sure I follow.

Meaning

I don't fully understand.

Translation language

John: The new algorithm involves a complex series of calculations.
Alice: Can you explain it simply?
John: I tried to. <b>I'm not entirely sure I follow</b> myself.
Alice: Let's go back to the basics. Then, perhaps you can explain it more clearly. Now, <b>I'm not entirely sure I follow.</b>