Block purging or pruning in Leaderlog

I recently ran a leaderlog just before the next epoch.
It showed I was due to get 5 blocks - which was more than expected.
Later when into that epoch in gLiveView it showed Leader=8 - even better I thought but somewhat odd.
I ran leaderlog again and got the message 'block purging 5 blocks" (or was it pruning)
Indeed that’s what happened, back down to 3 blocks and that’s all I got.
I’ve never seen this before - block purging - can anyone shed light on this?