Hello,
I have some problem when I try to export a file which has a width of 2400px and a height of 600px.
When exported (PNG + Artboard selected), the dimensions are way bigger than in the original file (10000px/2500px)
Ilustrator is pretty new to me, so I have no idea how to solve this problem.
Sounds like you are exporting your png at 300ppi?
If it’s more than 72ppi, your image will get larger.
Pixels in Illustrator are just a linear measurement. Not really pixels. (at least that’s how I interpret them.) You can change the resolution on vector art when exporting.
Thank you! 
This solved the problem 