Not exactly equal, but somewhat close, for ref only:

MX13 to MX12 - Associate / Assistant Director (1 of 2)
MX12 to MX11 - Assistant Director (1 of 2)
MX11 to MX11a - Assistant Director (2 of 2)
MX11a to MX10 - Deputy Director (1 of 4)
MX10 to MX9 - Deputy Director (2 of 4)
....