Just a clarification: A here doesn't mean Angstroms. It means "number of nucleons", as in carbon-12 is an A=12 system.

So they're saying A>300 means "a quark system with >900 quarks"; normal protons and neutrons have three quarks a piece.

If I misinterpreted your comment and the above was already clear to you, please forgive my mistake (I didn't want anyone to confuse A for angstroms here).