I compared the GGA messages output by ublox GPS and xgps160. The number of satellites UBOX is using is 0-12. The maximum is 12, and xgps160 does not have this limit.
However, the number of satellites that ublox actually uses for calculation is greater than 12, which can be read from GSA messages. Therefore, it is recommended to read the number of locked satellites from the GSA message.