First Byte Time grade is better, but the speed is slower. How?

I’ve run two tests on the same URL using the same server proxy settings (From: Dulles, VA - Moto G4 - Chrome - Cable).

The first test, run 3/24/2020:
First Byte Time grade: F
1268 ms First Byte Time
555 ms Target First Byte Time

The second test, run 4/23/2020
First Byte Time grade: C
1464 ms First Byte Time
1146 ms Target First Byte Time

I imagine this is because the Target First Byte Time has changed. If so, what would be the reason for this change. This isn’t something configurable, correct?

The target takes the connection set-up time (dns, socket and tls) and then adds 1RTT + 100 MS. If the connection set-up in the second test was significantly slower (particularly the TCP connect which is used to estimate the RTT) then the target will shift.

Thank you!