It’s bum-fiffery. What kind of rock? How well will the penetrator penetrate aggregate, sand, shale, granite? Where’s the dang engineers to make this a useful graphic?
It is a generalized comparison to past weapons.
It is not an engineering specification or sale brochure and never pretended to be one.
Many of military and ex-military engineer-types prefer to keep our mouths shut about actual numbers nad distances and dimensions.
WWII, the Grand Slam and Tallboy worked well (supersonic, very heavy conventionally-dropped bombs - see the example near Baltimore at the Armor Museum), but all too often, they did miss. Not by much, but by enough to reduce the effect, particularly against smaller targets like bridges.
B-36’s were last bombers I know of to drop the Grand Slam and its US-derivatives. Laser-aiming will improve accuracy, and conventional explosives reduce the political pressure against their use. Personally, I think the Grand Slam is prettier than these. (The C-130 super-daisy-cutter bomb is little more than box-on-a-pallet actually. It works, of course, against surface spread-out targets; it's just fugly.
I am not an engineer but I have read a bit about bunker busters.
I think you could use them in succession to hit the same spot to get down lower. This is certainly possible with GPS guidance or lasers.
Just a thought. These things are really nasty and the shockwave in an underground cavern would be devastating. Can you imagine one, two, three, and then four in the same spot? Each bomb working it’s way lower until the desired depth of destruction was achieved.