did I understand correctly, the first number is:
\(4\frac{2}{7}\)?
in other words, this would be:
\(\frac{4*7+2}{7} = \frac{30}{7}\)
and if you drink half of it, then we divide this number by 2:
\(\frac{15}{7}\)
because 30/2=15
so you would have
\(2 \frac{1}{7}\)
still more than a daily dose!