[BioC] weird total number of probset ids in MoGene 1.0 ST Array

[marek piatek (BI)]

Hi all,

I am getting a strange total number of affyids when importing data from MoGene arrays.
The Affymetrix specifications say:

Estimated Number of Genes: 28,853
Positive Control: 1,324
Negative Control: 5,222

Plus some hybridization Probes, Background Probes and Poly-A Control, but they don't give the numbers.
Basically in total from the specified numbers, there should be 35399 affyids. However when I'm reading in the CEL files I'm getting total number of 34760 affyids.

What might be the reason that I have different number of affyids that is stated on the Affymetrix specifications?

Thank you,
Mark