Q: Random user logging in ?

Hi,

So as the picture attached shows with the login accounting there has been a total of 259

238 are legit from me - However I am unsure of the other 21 times logged in as _mbsetupuser

Is this normal or common ? If not how do I rectify and investigate these log ins, and if it's normal could you please explain why it is, etc. I am the only on that uses this iMac computer and I only have one log in.

Thank you so much