Gap is the driver's best lap in a session against the fastest lap in their class in that same session (zero is fastest in class), shown as time lost and as a share of the lap, so conditions cancel out and tracks can be compared. Typical is the median session.
Thank you for your letter. This change is not recommended, as the Fiesta never came with this head on it in the US-market. A weight break was also given to this car earlier in 2020, and the PAC would like to see it campaigned more in that new configuration before considering any additional changes.