When you put a positive number in scientific notation, you move the decimal point to the left. So, to return the number back to it's original size, you have to move the decimal point to the right. And scientific notation is written as # times 10^#, to move the decimal point to the right, you have to have a positive exponent so that the 10 becomes 1,000,000,000,000,000 instead of .000000000000001.
Hope that makes sense.