A negative exponent does not mean that the number is negative. The expression is equal to $\displaystyle{{2}}^{{3}}\cdot{{6}}^{{-{{2}}}}\usepackage{cmbright}\Huge\$ , which in turn is equal to $\displaystyle{{2}}^{{3}}\cdot\frac{{1}}{{{6}}^{{2}}}\usepackage{cmbright}\Huge\$