The minimum and maximum values shown under in the dataset's source tab under statistics matches the max & min in the classification statistics. However, the mean values are different. How can this be?
Perhaps try Calculate Statistics (Data Management)—ArcGIS Pro | Documentation if the current skip factor you have is other than 1.
I don't think I need to set a skip factor, I would like all data in this raster to be evaluated.
Yep, I didn't suggest that. The skip factor on your dataset stats is listed in the properties, if it's other than 1 - perhaps try the tool. Some screengrabs might help others to better identify the issue also.
What is the difference?
What about nodata values?