Can you explain the uncertainty problem?

Problem 1-16 asked for the uncertainty on the time for the pulsar to rotate 1 million times. The uncertainty on the time $T$ to rotate once (i.e., the period) is $\delta = 0.00000000000003$ ms (the $\pm 3$ refers to the last decimal place of $T$). We found the fractional uncertainty, which is $\delta$ over $T$. The time to rotate $10^6$ times is $10^6$ times the period. The fractional uncertainty on that time will be the same as the fractional uncertainty on $T$. If we know the fractional uncertainty on a quantity, we can calculate the absolute uncertainty on the quantity by multiplying the fractional uncertainty by the quantity.