There was time on the back straight at Snetterton to have a look and add that time to the split time you had a look at coming up the start finish straight.
The GET one I had (and probably all GPS ones) let you set splits. Mine would flash a green or Red LED as you passed the split and tell you how much up/down you were on that split (to your best lap). It was nice I keep seeing that green LED in the bottom of your vision as you worked your way through the first session.