Will 7m, or so, at that depth (about a mile, for imperialists🙂 ) cause any subsequent settlement at the surface? I might guess not, but thinner seams of coal have led to subsidence in some areas.
I know they haven’t taken any coal (about a million tonnes?) from beneath Bolsover Castle. Grandfather took the ‘easy seams’ and the one I went along was only around one metre thick but less than 400m underground.
They took as much coal as they could get and allowed the roof to collapse behind the coal face with mechanical extraction. I didn’t have to actually crawl along the face but a severe ‘stoop’ was necessary to negotiate the hydraulic props behind the cutter. Some in our party were on their hands and knees all the way along the face!