each theater is a little different depending on who designed it.
more than likely it is Orcestra Levels, Row A Seat 39.
Is there a multi level area that is not a balcony? or is the Orcestra Level organized into Areas, maybe Area S.
Or it could be just Box Office Jargon that for some reason prints out as such.
If you really want to impress your date, take a few minutes and run by the Box Office and ask the girl at the ticket window or wait until show night and specifically seek out an Usher.
I doubt there is any theatre that would list a location such as Left side. Theatre directions are always misleading to those that are not oriented in theatre jargon. Stage Left means to the left as you are on the Stage. House Left means to the left as you are in the House looking at the stage.
SIDENOTE: If it's a musical, I do not recommend Front Row seating. You will be watching the actor's shoes mostly. I would definitely seek out about 5th row from the stage of so. Go for Center of the open area. The sound is balanced for quality from the installers to center.
oh and your pdf file did not come through the Answers site. Can you add a link to the theatre website. I will definitely be able to help if I know which theatre you are talking about.