Upon taking a closer look at the account, it looks like calls made to multiple tracking numbers from the same number are being attributed to the first source (tracking number). This is why you can’t view which tracking numbers are associated with each voicemail in Lead Center. As a workaround, you are able to cross-reference the voicemails in Lead Center with your Call Log. The Call Log view should pull exactly which tracking number was called, no matter if you called each from the same number.
All that being said, I can see how the current setup is confusing, and I’ll absolutely share this feedback with our product team.