It can be either age because the Matchmaker starts to visit your tama after a specific number of hours after it evolved into it's adult character, not a specific age in years.
Same as evolution - where the baby is a baby for 1 hour, then evolves into a child for 24hrs, then evolves into a teen for 48hrs (V4+V4.5) or for 72hrs (V1-V3), then evolves into an adult...
The Matchmaker begins to visit 72hrs after your tama evolved into an adult - so depending on what time of day you started it as a baby and named it, it may have a different age showing on it's stats screen to another persons tama.
Don't worry, there's nothing unusual or different about your tama! Hope you find a good match for it