Yeah, that 13.0:1 cell is idle. Anything outside the boundries of the table will be linked to the nearest cell... so 500 RPM's @ 40 kPa would still be 13.0:1.

When you are first tuning it... keep it simple. A good target AFR to hit in vacuum is around 14-15:1 at first. Once you have a big part of the table ironed out you can easily switch it to best fuel economy by tweaking those vacuum cells leaner. You need the best resolution when the engine is changing RPM's and kPa's the most, which is during spoolup and around peak torque, you may have noticed that 3500 column which makes life a lot easier when trying to hit that perfect AFR when you are trying to spool as fast as possible.