manometer

[stan56]

Got this question in a past paper for a fluid mechanics exam,

Consider that a height difference of 1 cm in a fluid with s.g. =0.82 corresponds to a pressure difference of 80.3 Pa. What pressure difference corresponds to h=1cm when s.g1=0.81 and s.g.2=0.83? What is the increase in accuracy of a 2 fluid manometer relative to a single fluid manometer?

what I cant figure out or understand is the last part of the question i.e. the increase in accuracy of a 2 fluid manometer relative to a single fluid manometer. Can anyone explain to me how I work this out