New Holland TS100A HH Menu question

So to start out several years ago the fuel gauge started reading backwards out of nowhere and. Now just recently I have gone into the HH menu and changed an option under HB H3 LAP to yes and the gauge reads properly again. My question is what does lap mean because the service manual does not say anything about it.

Here is a link to a video of me changing the setting. filtered-571A2A11-4783-4AFA-B23E-9811883B1C4F.MP4