https://arstechnica.com/gadgets/2019/08/apple-releases-macos-10-14-6-supplemental-update-to-fix-sleeping-macs/

It was just over a week ago that Apple released macOS 10.14.6, but the company has already pushed out a Supplemental Update. Released today, the update fixes a heretofore not-widely-known issue involving sleep mode on Macs.

It seems at least some Macs have failed to wake up after going into sleep mode. The update doesn't seem to change much else. Apple's complete notes are as follows: