Histidine has $p{K}_a$ values of 1.8 (alpha-$\mathrm{COOH}$), 6.0 (imidazolium side chain, $+1\to 0$ on deprotonation) and 9.2 (alpha-$\mathrm{NH}{}_3{}^{+}$). The average net charge per molecule at pH 6.0, to the nearest 0.1, is

Below pH 1.8 the species is $+2$; between 1.8 and 6.0 it is $+1$; between 6.0 and 9.2 it is $0$ (the pI is 7.6). At pH 6.0 = $p{K}_a$ of the imidazolium, half the molecules are $+1$ and half are $0$, so the average is 0.50, i.e. $+0.5$ to one decimal (the other groups contribute under 0.01).