Lap time only stores 1 lap and doesn't subtract the previous so it's more like "save current time".
I believe the appropriate lap function should do this when pressed:
Also, I don't think it's possible in this version of the SDK but it would be great if you could save the start time into permanent memory so you could return to the timer later with it still going.
Edit: Some more thoughts.
I feel the space in the "skeuomorphic design" would be better used for multiple lap times or lap time differences etc. Obviously it removes the aesthetic, I guess it's up to opinion: form or function.
Also I think when it gets to "hours" you probably shouldn't be showing the milliseconds, all those screen updates can't be good for battery.