XDs 9mm vs PPS 9mm capacities

Hoping someone can clear up a question for me.

The Springfield XDs 9mm and Walther PPS 9mm, both with the flush-fitting magazines, have the following published dimensions.

OAL: 6.3"
Height: 4.4"
Width: 0.9"

Identical dimensions. However, the XDs holds 7 rounds of 9mm, and the PPS holds 6 rounds (again, with the flush-fitting magazines).

What is this black magic? How does the XDs fit an extra round in? Initially my thought was that the "width" is not actually the same, that the XDs must be a little wider. Maybe the PPS publishes the spec including the levers, and the Springfield doesn't?

Anyone have experience with both guns that can chime in?

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