Can someone explain why the "Stage 1 speed" at the top right on the technical broadcast stream jumps from 6,000 km/h to 24,000 km/h right after the separation?

Can someone explain why the "Stage 1 speed" at the top right on the technical broadcast stream jumps from 6,000 km/h to 24,000 km/h right after the separation? https://youtube.com/watch?v=PFoOqqSIYpw https://youtube.com/watch?v=PFoOqqSIYpw around 22:28 mark In fact, the speed settles at 18,000 km/h after the landing.