If your date and (or) time of the unit differs significantly from the current time, then either your tracker saves the data to a black box and then sends it in batches, or you have incorrectly configured timezone on the tracker.
Please be sure to set the namezone 0 (UTС) on the tracker, regardless of your location, if you currently have a different time zone installed. Then you may have to wait throughout the day for the data to start updating correctly according to the new time zone.
The time zone can be set using the SMS command, and for some tracker models also in the unit menu - Tools - Setbox.
If you are interested in fuel related commands, you can check if there are such commands for your tracker model in the unit menu - Tools - Setbox. If the commands you are interested in are not there, but your tracker has them (except for the Legacy category trackers), then please write about them in more detail and we may be able to add them.
Please write about your other questions in more detail.