The South wanted to count all slaves as full votes for purposes of apportionment of the representatives. Doing so, they would be permitted more Representatives.
By holding that vote to 3/5, it empowered the North to have a greater apportionment of representatives that would be anti-slavery.
In the context of the time, the 3/5 provision was a victory for anti-slavery forces.
However, looked at with no context, it looks like slaves were not valued as people.
This was a political tactic by the northern colonies to try to obtain a greater share of power in Congress.
Too bad the North was all slave, except MA, at the time of the Constitution passage.