Call the groups A and B and number the teams 1 to 8.
Groups A and B each play 28 matches within their individual group (1v2, 1v3, ..., 1v8, 2v3, 2v4, ..., 2v8, 3v4, ..., 7v8=28 matches: 7+6+5+4+3+2+1). So 56 matches are played altogether.
The top 4 of each group are called A1-A4 and B1-B4 in the Super 8. The matches are:
A1vB1, ..., A1vB4, A2vB1, ..., A2vB4, ..., A4vB4=16 matches.
So far we have 56+16=74 matches.
In the semifinals we have A1, A2, B1, B2. There are 4 matches: A1vB1, A1vB2, A2vB1, A2vB2. That makes 78 matches.
The final is played between A1 and B1 winners, making 79 matches in all.