Problemas con las llamadas entrantes

hello good morning.
We are telecommunications students and we were working with vitalPBX. We had a problem, where when filling out all the fields, as shown in the first image, incoming calls did not work, but outgoing calls did. We went to the inbound calls section, and at the end in the inbound destination section where you have to choose the extension where you want the call to arrive, we set it to go to extension 102.
We were investigating in the trunks section and at the bottom where contact user appears we put the user number. At first it didn’t work. In that same section we tried putting the extension where we wanted the call to arrive and it worked. The question is, why if in the incoming calls section it appears to dial the destination it is canceled with the contact user of the trunks? Or why do you have to put the destination of the call in the contact user?
Now we attach two images so you can see what we put.