The positive exponent of 10 is the number of places you need to move the decimal point left to get the number in the form d.f...f × 10ⁿ where d is some non-zero digit, and the digits f are those necessary to express the full precision of the number. Moving the decimal point to the right will produce negative values of n.
1 = 1 × 10⁰
27.5 = 2.75 × 10¹