thumb and digit for one note head - guitar

[Albert Einstein]

In lilypond 2.4.2 manual 5.7.10 Fingering instructions is given:

You can use the thumb-script to indicate that a note should be played
with the thumb (e.g., in cello music) 

             <a_\thumb a'-3>8 <b_\thumb b'-3>
        
        [image of music]
        
        
        
        What in case to put for one note head thumb and digit for
        example to instruct left and right hand for guitar (left third
        finger, right hand thumb) ?
        
        When i write <a_thumb-3 a'> result is the same like in manual?
        
        ALbert