First, I think you mean:
3.123423e-07
That is a number in scientific notation, meaning:
1 digit to the left of the decimal point
as many digits as necessary to the right of the decimal
followed by the letter "e"
and an exponent to tell you where the decimal point *should be*
In your case, the actual number is:
0.0000003123423
You'll see that number if you set the number format to anything other than
General or Scientific and set the decimal places to 13.
Does that help?
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Regards,
Ron