[Plugin: NextGEN Gallery] Single Pictures Change Size

I have two different screenshot posts with the same dimensions set for their single image:

[singlepic=808,620,370,center] (https://scrawlfx.com/2008/05/gothic-iv-first-ten-screenshots/)

[singlepic=318,620,370,center] (https://scrawlfx.com/2008/05/race-driver-grid-gets-three-new-screenshots/)

The images change sizes though, they are not the 620×370 that I wanted them to be though. Same goes for the little images in the Gothic IV post, one of the images in the little screenshots is bigger than the rest even though I set them all the same.