The second 1 in 15.186 is the one to the right of the decimal point, so the value is 1 tenth or 1/10.
Remember that when you're working with decimals the numbers to the right of the period go like this: Tenths, hundredths, thousandths and so on. So the total value of the numbers to the right of the decimal point is 186 thousandths or 186/1000.
