The margin of error of the 99.7% confidence interval is

This computed margin or error is actually 3 standard deviations from the mean according to the empirical rule. The empirical rule states that 3 standard deviations away from the mean constitute the 99.7%.
Therefore, the value 0.066 is 3 times the standard deviation. The standard deviation, SE, is

The standard deviation is
0.022.