To me, (and I admit to not being into these money/finance problems), it looks like the 0.005 is an approximation to my 0.00486755
It possibly comes from the binomial expansion of (1 + r/100)^12.
\(\displaystyle \left(1+\frac{r}{100}\right)^{12}=1+12\frac{r}{100}+\frac{12.11}{2!}\left(\frac{r}{100}\right)^{2}+\frac{12.11.10}{3!}\left(\frac{r}{100}\right)^{3}+\dots\) .
Provided r/100 is small, we can say that
\(\displaystyle 1+12\frac{r}{100} \approx 1.06\), so \(\displaystyle \frac{r}{100} \approx \frac{0.06}{12}=0.005\) .
Tiggsy.