Past Bobo Project

Math whiz needed for Time-weighted Return explanation for $25

Good day. I am struggling with the logic behind the attached spreadsheet. The spreadsheet shows two individual investment accounts (client 1 and client 2) and then the combined (client 1 + 2) at the top.

My confusion is how the combined return can be higher than either of the individual returns.

IMPORTANTLY, I need the explanation in very simple terms.

Thank you for your consideration.