3-7 million is somewhat proportional to the # of TI 99/4a (my first computer) which sold 2.5Million or so, but many of those were probably on the fire sale, and

3-7 million is somewhat proportional to the # of TI 99/4a (my first computer) which sold 2.5Million or so, but many of those were probably on the fire sale, and at least some of them probably went to backup parts for people that already had it. While the 99/4a is remembered somewhat fondly by those who had it (speech synthesizer, expansion modules for p-code, forth and others), it wasn't a system that had a huge amount of development done for it, and died a pretty quick death.