What does this equation mean?

Everything above concerns $N_\perp$[$\Gamma$] , a bound on unitary orthogonalizations, which cost no minimum heat in principle: a sequence of reversible gates can in principle run adiabatically, with no thermodynamic floor at all beyond the ordinary Levitin-Toffoli rate. Reading out a result, however, generally requires erasing or resetting some register, and that step is bound by a different and independent piece of physics, Landauer’s principle: erasing one bit at local temperature T costs at least $k_B$T$\ln$2 of dissipated heat [ 6 ] , made precise with finite-size corrections by Reeb and Wolf [ 7 ] . This bound does not care about horizons at all except through whatever value T takes locally — which, per the cooling analysis above, only becomes horizon-dominated at the sub-nuclear clearances where the acceleration bill has already made the scenario moot.