Convert 0..489 to scientific notation

I do not understand why there are two decimal places.
But either ways if you are asking for :
0.0000489 then it is 4.89*10⁻⁵
0.489 then it is 4.89*10⁻¹
The trick is to count the zeroes to the first actual significant number you see and then write the number you counted with a negative sign for your power. 
I hope this helps!