How do I control the preview of an Illustrator file?

[MarieMeyer]

What settings control the appearance of the preview image of an Illustrator file? I always assumed it was the first artboard. However, look at this screenshot. They are both Illustrator files. The artboard for the file on the left is 4" x 4"; for the file on the right it is 1.7" x 1.7". Since they are being previewed in the opposite ratio in Bridge, there must be some other setting that influences the outcome. Can anyone tell me what it is and where to find it?

[Ton Frederiks]

There are a couple of preference settings in Bridge for previews, Thumbnails and Advanced.

Try saving the [Converted] again as a recent CC version,