There's also the 'chord symbols reflect implied tonality' clue. For ease and simplicity, it's all written as if the guitar is tuned to ordinary open G tuning, except for some reason, it needs to be tuned a semitone higher. I can't really understand why - it'll sound (to most of us) just as good in open G.
It's good to have the proper dots as well, as it helps clarify timing, so if one reads that too, it takes some guesswork away. It could, if the sounded key really needs to be A♭, be played with basic open G tuning, putting capo on fret 1, and adding one to each tab number shown. There would still be that 'open string' sound. Or tune to open G, and play as writ, putting it actually in key G.