If the work carried out on your instrument qualifies for this extra service, it means that for a period of three months after the work was completed you will be entitled to any readjustments totally free of charge (excluding strings).
This is intended to accommodate any "settling in" of the instrument after major work or due to annual climate changes. You may also find that after you have become re-accustomed to your guitar after a period of time, you might prefer the action to be higher or lower or perhaps would like to try a different gauge of strings.
Whatever... just phone me!
Please do not try to alter the setup work performed on your instrument yourself before bringing it in for re-adjustment! The re-adjustment service may not be available free of charge if there is evidence of "fiddling about" by wannabee guitar technicians or mates down the pub who "know what they are doing"!!!... (Believe me... I CAN tell!!)