Kerning lock question

Hi,

I have read the tutorial (and apologies if I have missed the answer there) but what is the behaviour of the third kerning lock to the left?

I understand the other locks create kerning exceptions to their group.

That is the right lock that you would see when you move the cursor one to the left.

ah this makes sense. Sorry I thought it had a higher significance.

Thank you for clarifying as always.