For example, an L27(3^13) means that the design has 27 runs and 13 factors with 3 levels.
If your notation is L (number ^ exponent number ^ exponent) then you have a mixed-level design. For example, an L18 (2^1 3^7) means that the design has 18 runs, 1 factor with 2 levels, and 7 factors with 3 levels.