Not got my eqc yet but drive an eclass with the same tech. The car uses a mixture of signs read by the camera and sat nav data. So here in France it can be quite confused as our national speed limit was dropped in 2018 to be revised on a local level in 2019. So if you join a dept road between signs it maybe 80 or 90km depending on the dept and their view of the road ie a major route. So the car using sat nav currently will show 80 until it sees a sign saying 90.....an update of the sat nav has changed some routes up to 90 but not all as the authorities are all moving at different speeds in their reviews. All a bit of a pain but the answer to your question may lie in how the car is identifying the sp Ed at the time you see it ie panel or sat nav🤷♀️