Layer between ring beam and foot purlin, what is that?

Hello everyone, tomorrow the roof will be repaired at our place. I have now noticed a strange layer between the wall plate and the ring beam (?). Is that mortar? It sounded a bit hollow. From bottom to top - ring beam -> strange layer -> black thick sheet (roofing felt?) -> wall plate:

Sliding layer because concrete and wood expand differently

That was indeed concrete that was protruding over the formwork for height compensation.

That was indeed concrete that was sticking out over the formwork to level the height.

I had recommended you to relax ;) Rhineland greetings