Does anyone know why laps are odd times/distances on a workout?

Hi - I've been trying to work out why I'm getting odd lap notifications when I'm doing (for example) interval workouts as part of the marathon training plan.

The watch is giving me alerts like this one (I was at about 7km at this stage) - but lap 10??

 

When I check the splits I can see the same weird irregular laps.

Some of the alerts are for the 1km distances (which is how I have it set up) and rest just seem random.

Any clues?