The dispute that happened during the Philadelphia Convention of 1787 was distributing the House of Representatives based on the population of that state.
During this time, the North and the South were arguing about whether or not slaves should count towards the population of that state. If you had a bigger population, you would get more House of Representatives in Congress. Slaves were not equally seen as people, so some thought slaves should count towards the population, while some did not.
The Three-Fifths Compromise solved this. This made it so every five slaves counted as three people in terms of counting the population. This was good for the South, as it meant they would have a greater population and more House of Representatives.