The first 3 numbers (from left to right) are the ones counted as 3 significant figures. You alreadty start of 5 significant figures. What you do is count the numbers, from left to right, and once you get to the number you're finding (in this case the 3rd significant figure), then you look at the number to the right of it and see if it's over or under 5. Depending on which one it is will determine wiether you round up or stay at the same point.
