I don't think the tab is right at all--

First-the guitar is in D-down tuning, which is how you get that first low note(use palm to damp the string, Blues-style)

Then you do hammer on the open G string up to an A(second fret), but it sound to me like it goes from there to the C, first string, and back to the A--

I found that I could do the whole lick easily by:

holding my hand in the F-chord position,

hammering on to the A (G-string, 2nd fret)

then hitting the C (first fret, B string)

Back to the A note

Then catch an F note on the D string(third fret)

And then hitting C , third fret on the A string--


Don't let the other guitars fool you into trying to play their parts--this is a simple lick--

Thanks for bring it up--it's been a while since I've listened to it, and it is a great tune, played well--