Phrases Asking for Clarification

I'm not entirely sure I follow.

C1

Meaning

I don't fully understand.

Example sentences

John: The new algorithm involves a complex series of calculations.

Alice: Can you explain it simply?

John: I tried to. I'm not entirely sure I follow myself.

Alice: Let's go back to the basics. Then, perhaps you can explain it more clearly. Now, I'm not entirely sure I follow.