Subtract the two numbers as you normally would, then determine the number of s.f. you are allowed. In addition and subtraction, the answer may not have more s.f. than the least significant number to the right of the decimal. There are four places in 0.6260 and 3 places in 0.015. Therefore, the final answer should be rounded to the nearest thousandths (0.001 or three places to the right of the decimal).
