The PNG export settings options are similar to the PNG publish settings options (which you can apply as well), with the following exceptions:

Dimensions

Sets the size of the exported bitmap image to the number of pixels you enter in the Width and Height fields.

Resolution

Enter a resolution in dpi. To use the screen resolution and maintain the aspect ratio of your original image, select Match Screen.

Colors

The same as the Bit Depth option in the PNG Publish Settings tab and sets the number of bits per pixel to use in creating the image. For a 256‑color image, select 8‑bit; for thousands of colors, select 24‑bpc; for thousands of colors with transparency (32 bpc) select 24‑bpc with Alpha. The higher the bit depth, the larger the file.

Include

Select to export the minimum image area or specify the full document size.

Filter

Options match those in the PNG Publish Settings tab.