Merging multiple raster files incorrect value in ArcGIS

I have multiple rasters in .tif (geotiff) format and I´m trying to merge them into one using the Mosaic to New raster tool in ArcGIS(10.7.1). These rasters have a partial overlap between them and are 16bit unsigned int values.

When i merge them using the Mosaic to New raster tool with proper folder locations, the merged file name (something.tif), pixel type (16 bit unsigned int), number of bands (4 – R, G, B and NIR), Mosaic operator (last) and mosaic colourmap (first) selected i get a new raster whose values are sometimes different than the underlying rasters in a few pixels.

For example, these are the values for a colocated pixel:
Merged raster: 919,1182,619
Raster 1: 883,1124,631
Raster 2:912,1163,668

The merged raster values are very close to the underlying raster in some pixels and same values in some pixels but shouldn´t it be the same as the last raster encountered throughout the image? Why is it different?

I´ve attached images of these pixel values along with some info on the merge function i ran.