Hi vee, welcome!
The time values of the tabs is a subject that has yet to be raised, so thanks for posting it.
It used to be that tablature was restricted to just the fret number and string, with no time values for anything. You were, I guess, expected to figure that side of things out by ear. The program I use,
GuitarPro, actually does asign time values, just like conventional notation, so it has come a long way since the old days of text based tab.
Below is an image which should help. It's all of an A note; The first bar is a whole note, the second is two half notes, then four quarter notes, then eight eighth notes and 16 sixteenths.
It follows the same convention as notation, as far as I can tell. I hope that answers your question. A dot after any of them increases the time value by half.