@victoria, are you using the MobilePush SDK? If so, what platform & version are you implementing?
The deviceId value is automatically generated as a unique identifier by the SDK and sent to the server for association with the contact. It is an internal value.
A system token is generated and passed by your application code to the SDK.
Does your application call our setContactKey() method? Is that using a unique value per device/user?
If necessary, I suggest you open a support case with your Marketing Cloud rep so that we @murilo, in addition to gathering the information Seth has requested, please be sure to log a support request with your Marketing Cloud representative.
We will be much better able to track, respond and be held accountable to you (and all our customers) needs via customer support.
Of course, continue to raise questions and concerns here - the MobilePush SDK team is happy to help in any way we can.