It is a logarithmic scale that shows 10 ⋅ ⋅ log 10 second instead of second. For example, one microsecond is 10 ⋅ ⋅ log 10 ⁡ ⁡ 0.000001 = 10 ⋅ ⋅ ( − − 6 ) = − − 60 . To convert −30 read on the scale to second calculate 10 − − 30 10 = 10 − − 3 = 0.001 second = one millisecond. On a logarithmic time scale a step lasts ten times longer than the previous step.