Timing pull is hard to describe, but the numbers are basically an indication of how many degrees over-advanced the ignition timing is.
Ideally you want around 1 degree of pull on every cylinder throughout the entire rpm range. This means that you are slightly over advanced, but more importantly not under advanced (or too retarded
)
If you have 0 timing pull then you may be underadvanced meaning you are not achieving peak VE (volumetric efficiency) or in simple terms the fuel being used, is not being used to its maximum potential.
Getting maximum VE isnt easy on a production engine and requires individual cylinder injection and timing adjustment, this allows you to tune each cylinder as an individual engine.