Reduction or increase in microbial counts is often expressed in Log base 10. This is the number of times 10 must be multiplied by itself to equal a certain number. For example, Log2 is 10X10=100. Log3 is 10X10X10=1000. This is also expressed as 103. A more simplified explanation is to use the superscript number to determine the number of zeros that will follow 1. 105 would be 1 + 5 zeros or 1+ 00000 = 100,000. Application: A prep solution produced a 4Log reduction on a skin surface that had a million (106) organisms per cm2. That means that 4Log or Log4 or L4 or 104 equals 10X10X10X10=10,000 organisms killed. Subtract that from the original one million organisms per cm2 and you have 106-104=102 or 100 microorganisms per cm2 left.