Stencil apertures - is it a bug or a feature?

Hello JLPCB support,

the last stencils we ordered have shown different apertures for the Pads on nearly all openings of the stencil, but not all.

To show it, I superimposed the original Gerber with the production Gerber I downloaded afterwards:

Red is your production file, green the submitted Gerber.

The online preview of the the calculator also shows the Pads as we have drawn them (in grey):

Is this a Bug, or is it a feature?

Thank you very much,

Guenter Thelen.