If the esxcli command that you've most likely used for the update returned " The update completed successfully, but the system needs to be rebooted for the changes to be effective.", and you see "(Updated) ESXi-6.7.0-20191204001-standard (VMware, Inc.)" after the reboot, then your installation was successful.
If you want to verify, you may either compare the installed packages (visible in the GUI) with e.g. https://esxi-patches.v-front.de/vm-6.7.0.html. Alternatively you may run the update command again, but with "--dry-run" appended to the command line, and check the command's output (Installed vibs, Removed vibs).