My setting states "Your Mac is up to date-macOS Monterey 12.5.1.

no. you don't put 15.6.1 on your Mac.

macOS 12.5.1 is the current version of macOS Monterey. if that is what you have on the MacBook, then it is fully up to date.

iOS is for the phone. and if you have 15.6.1 on the phone, then it too is fully up to date.

macOS updates / upgrades are for macs

iOS updates / upgrades are for phones.

they are totally independent from one another. although it's best to keep both current on their respective devices.

12.5.1 is the current monterey version.

15.6.1 is the current version of iOS for your iPhone. if that is what you are trying to accomplish, please use your phone and go to "Settings > General > Software Update" to update the phone.

if that's not what you are asking, please read Writing an effective Apple Support Communities Question and restate your question in detail.