There are two forms of team rankings - Normal and Olympic system. In both systems, top 3 players' ranks from each NOC are considered and matches between all the NOC are simulated.
Normal rankings are used for World Championships and other team tournaments because the playing system is best of 5 single matches viz : A v X, B v Y, C v Z, A v Y, B v X. Virtual matches are simulated between all NOCs, the NOC which wins a virtual match gets 2 points and the other NOC gets zero.
For example, if top 3 players of NOC1 is 52, 65, 89 and for NOC2 is 43, 78, 81 then by the playing system the results of virtual matches is given below
52 vs 43 NOC2 wins
65 vs 78 NOC1 wins
89 vs 81 NOC2 wins
52 vs 78 NOC1 wins
65 vs 43 NOC2 wins
So NOC2 wins the virtual duel 3-2 and gets 2 points and NOC1 gets 0. Similar simulations occur between all NOCs and they are ranked based on the points garnered
If one notices since China has the best 5 men's singles players, it should win all virtual matches and hence it garnered 296 points as number of NOCs is 149
Olympic rankings are used for Olympic Games only and the playing system is BC vs YZ, A vs X, C vs Z, A vs Y, B vs X ie there are 4 singles matches and one doubles match.
On a sidenote, India's ranking has been consistently been around 11th-13th because its top 2 players, Sathiyan and Achanta have been in the 30-40 rank range but the third ranked player was always above 100. The ranking leaped to 8th now because Harmeet Desai improved his ranking from 104 to 84