This implies that 3/10 inches on the map represents 7/8 miles on actual distance
Conversion Unit
This conversion unit or rate is used to assist use to represent larger values on a smaller piece of paper in this case map. The conversion rate between inches and miles is

Data given
What this implies is that we would represent 7/8 miles of actual distance by 3/10 inches on the map. This would definitely reduce the size or length of the paper required.