Inverse log is just raising 10(or the 'base') to the the number
LOG(23) = 1.3617 'inverse' log(1.3617) = 10^(1.3617) = 23
For natural ln use the 'e' function..... ln(23) = 3.1354 'inverse' ln = e^(3.1355) = 23
log2 8 = 3 'inverse' log2 (3) = 2^3 = 8