It seems that the provided coordinates in the JPW world file represents a map on the Universal Transverse Mercator coordinate system (UTM) and I am afraid that currently the map control does not support this projection.
As a side note, the GeoBounds properties of the map and the MapProvider serve different purposes in RadMap. The RadMap.GeoBounds restricts panning region, while the MapProvider.GeoBounds limits the size of the geographical region covered by the respective provider and allows creation of specific “map windows” over the map.
About your question, unfortunately without the files (image of the map and the data) and your implementation I cannot be sure why the coordinates differs then the defined in the rect. A possible reason could be if the aspect ratio of the loaded image (pixel width/pixel height) do not correspond to the projection that is used.
You can take a look at the following resources that could be helpful for your requirement:
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