jpeg export Illustrator, keeping pixels AND ppi

Hi there,

I designed a cover in Illustrator and now need to export it like this: jpeg, RGB, 2400 px width, 300 ppi. The artboard is already the right size (2400 px width) and I thought if I export it and add 300 ppi in the "scale" box, it would come out right. For some reason tthe ppi are correct (300) but the image size has turned 4 times as big (10 000 pixels width). Why does this happen? How can I export it in the right pixel size AND 300 ppi? FYI if I make the artboard smaller (576 pixel) and export with 300ppi then it turns out right, with 2400 px width. But that can't be the right workflow?

I also checked that my raster effects of the document are set to 300 ppi.