Anna writes reports packed with statistics, and she cannot stand fractions. Instead of writing 56/87 she writes the decimal form 0.64367816091954022...
That creates two problems. The decimal form usually has to be cut off somewhere, and once it is cut off it is no longer equal to the fraction. Anna keeps the second problem small with one rule: she writes the decimal form up to but not including the first digit that is 0 or 9, rounding down when that digit is 0 and rounding up when it is 9.
Under that rule 56/87=0.643678160919... becomes 0.64367816, and 55/87=0.6321839080459... becomes 0.632184. When the very first digit after the decimal point is 0, as in 1/87, Anna writes just 0. When the very first digit after the decimal point is 9, as in 86/87, she writes just 1. When neither 0 nor 9 ever appears in the decimal form, as in 58/87, Anna throws the value out.
The decimal form is the one long division produces, so a fraction that terminates is followed by zeros forever. 1/2 is 0.5000..., and Anna writes it as 0.5.