"E" stands for exponent, specifically 10. If something says "E+38" (like in Microsoft Excel), that means 10^38 in scientific notation.
Therefore, "-3.4 E + 38" means -3.4x10^38.
The "+38" means there are 38 zeros following a 1 as the exponent. It also works with negative numbers. For example, E-3 equals 10^-3