Gained a few pixels

Finally got editing support from C One for my new A7RIVA and I'm finding something funny with my frame widths.
It's supposed to be 9504x6336 pixels and that's indeed what C One is giving me as a default....unless I manually adjust the crop and all of a sudden I can boost things up to 10122x6561. That's 66.4Mp in what should be a 61Mp camera

Guess this is the illusive total vs effective pixel counts, far edges doesn't look bad in any way.

Here's a screenshot out of C One without increasing the "crop" to unconstrained.

a7riva by Johan Olsson, on Flickr

Doesn't seem to work for all shots but the majority seem to allow it.

Got an explanation from DP Review, it's just how C One handles distortion correction.
With some lenses it stretches the image slightly while some compresses the image, hence why all the shots using the 24-105G at 24mm allows the "stretch" and something like the 70-200G at 200mm compresses the image slightly.