Tamagotchis can become adults at any age - they just have ot be teenagers for 72 unpaused hours! So if your Tamagotchi became a teenager when it was 0, it could be an adult when it is only 2 or 3! The age counter doesn't really matter, it can be messed up by pausing, resetting and downloading etc.
The matchmaker comes 72 hours after your Tamagotchi changes into an adult, again, the age counter doesn't really matter.