Illustrator - Artboard Issue

Domenico,

In addition to the questions from Doug, which downscaling would give you the size you expected (my first guess would be scaling down to 24%, corresponding to the difference between 72PPI and 300PPI)?

In other words, the unexpected might be expectable.

Please add some detail.

What size is your document?

What format are you exporting?

What method are you using to export?

What size are you getting that is not correct? What do you use to check the size?

Please include screenshots and/or the exported result.