What does 5.8E-12 mean?

The E stands for times 10 to the power of

For example 200 could be written 2x10^2 which would be written as 2E2 or 2E+2 in scientific notation.

The one you found - 5.8E-12 means - 5.8x10^-12 which is the same as - 5.8 * (00000000001) or

000000000058