If it is in the bottom left hand corner of the screen then it is the speed limit for the road you are on. It should read 30, 40 50 etc. However if you get 19, 25, 31 etc then that's the mph reading as kph i.e in a 30mph zone then it would display 19 which is what 30kph is in mph. Sounds complicated but this was a problem I had when I first had my car and after a number of months they came up with a software update and now it reads the correct figures.
2010 60reg C-Max Titanium 1.6 Ti-VCT, Dark Micastone with Convenience & Family packs.