lvl peramiters dont work

i was testing command block commands when i realised that the lvl peramiters dident work, i tried lowering my lvl below the minimum and rising it above the maximum i even changed @a[ml10l10} to @r[ml10l10] and even @p[ml10l10] i also tested with @a[ml20l20] and @a[ml10l11] but nothing fixed it so thats why im typing this...