[Gimp-user] Gimp exporting png gif and jpg at reduced size

[PeterBez <forums gimpusers com>]

I wonder if anyone can please help me again.
All I want to do is export an image as either a .jpg .png or .gif for a web
banner at a size of 640px x 100px at 72dpi.  When I do the export I get an image
that measures 225px x 35px.

The canvas size is correct at 640 x 100 x 72

I cannot find what I am doing wrong, even exporting a single coloured layer
gives the same results.

This is a simple task in Photoshop.

-- 
PeterBez (via www.gimpusers.com/forums)