"Target EGT" isn't really a thing -- it's highly dependent on the placement of your EGT probes, so comparing installation to installation isn't particularly meaningful, and even cylinder to cylinder on your own plane may not be a valid comparison if placement is slightly different.
That said, cylinder 4's CHT being so low, combined with low EGT, while you appear to be at cruise power stands out to me to suggest something's not quite right. I'd be suspicious of a dead spark plug (or wire) on one ignition in cylinder 4 than anything else.
1) When doing a mag check, do EGTs rise on all four cylinders when on each ignition? If you have a dead plug, you'll get an EGT drop on cylinder 4 on one of your ignitions (and the engine will run noticeably rough).
2) Do a GAMI lean test. If you don't have instrumentation problems and the cylinder is just richer than others, you should still get a peak that's similar to the other cylinders, just at a much lower fuel flow.