Let's take as an example South Africa's net run-rate in the 1999 World Cup. South Africa's listing in the Group A points table published in the group stages was as follows:
P W L NR T Pts Net-RR For Aga
South Africa 3 3 - - - 6 +1.495 678/147.2 466/150
The columns we are looking at here are the last three: "Net-RR", "For" and "Aga". The figure in the "Net-RR" column is achieved by subtracting the answer of the division in the "Aga" column from the answer to the division in the "For" column.
To use this example:
South Africa had scored, so far in the tournament:
Against India, 254 runs (for 6 wkts) from 47.2 overs
Against Sri Lanka, 199 runs (for 9 wkts) from 50 overs
Against England, 225 runs (for 7 wkts) from 50 overs
Across the three games, South Africa scored 678 runs in a total of 147 overs and 2 balls (actually 147.333 overs), a rate of 678/147.333 or 4.602 rpo.
Teams opposing South Africa scored:
India, 253 (for 5 wkts) from 50 overs.
Sri Lanka, 110 all out from 35.2 overs.
England, 103 all out from 41 overs.
In the case of Sri Lanka and England, because they were all out before their allotted 50 overs expired, the run rate is calculated as if they had scored their runs over the full 50 overs.
Therefore, the run-rate scored against South Africa across the first three games is calculated on the basis of 466 runs in a total of 50 + 50 + 50 = 150 overs, a rate of 466/150 or 3.107 rpo.
The net run-rate is, therefore,
4.602 Run-rate for
3.107 Run-rate against