Answered below at your first post.
so this is right, each number can only have two digits
for f. should it be 10 or 10.
10 isn't right. It should be written as 10. or as 1.0 x 10^1. Most texts will tell you to write it as 1.0 x 10^1 no matter what but most people I know accept 10. as ok since that clearly shows where the decimal point is to be placed. Of course, it you are writing a sentence and the period after the zero comes at the end of the sentence, then we don't know if we "dot" we have there is the period or to show two significant figures. In that case it is a must that we write 1.0 x 10^1. That way there is no doubt.
answered 1 note above.