I would report it as 0.015 f/ml as it is not less than 0.010, so 3 decimal places.
A1.43 The concentration result must be calculated and recorded correct to the appropriate
number of decimal places, depending on the reasons for sampling and the decision being made;
eg to determine whether the 0.1 f/ml control limit is exceeded, calculate and report to 2 decimal
places. For the clearance indicator where the fibre level should be less than 0.010 f/ml, calculate and report the result to 3 decimal places.