its a pattern. the top goes up by three's so if it goes from 12 to 30 the d8 should go to 20 because if you add 3 to 12 to get it higher than you add 2 to 8 to get it higher.
If the contents of a cell in a spreadsheet are as shown below. 7.5540794E-6, the content of the cell will represent 0.0000075540794.
The standard form 7.5540794E-6 was converted to decimal number by shifting the decimal point to the back 6times since the power of the multiple of 10 is a negative number (-6) hence the reason for shifting the decimal point to the back 6times to have 0.0000075540794.