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

Web Performance Discuss Test Results
1

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?

2

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.

3

Thank you!