What do the numbers mean?

[Zac67]

The 1000 was renamed just that only after the 500 and 2000 were announced.

I'd guess they positioned the '1000' as a base number to start from (with '100' offering too little options and not showing enough distinction from '64' and '128'). So they could use lower numbers (1000/2) for low end and higher numbers (1000*2) for high end machines. From that they counted up in hundreds and thousands with the 1200 hanging somewhere in between - low end target with higher performance than the older 1/2000.

[Zac67]

@amigadave

Before being called A1000 the first model was simply called "Amiga". I'm not entirely sure when it was renamed but that was at least a year after introduction.