OK.
However, it may be worth noting that the same imgae, saved to the same size in 4.5.4 had a predicted size of 43KB and a final result of 108KB. Larger than the prediction, but closer than 4.6.1 which resulted in 152KB.
I assume that the EXIF, IPTC, XMP, and ICC profile data is a known constant, certainly known for a given source image. It seems like it could be folded into the predicted size with a great deal of certainty.
For my usage in producing images for a web site the resulting size is important. If you're saying it's as good as it can be, then I have no choice but to accept that, but it's disappointing that the accuracy declined from 4.5.4 to 4.6.1.