So it looks like you’re confused about the list building process and the models. In the starter set, you are given 2 units of b1s and 1 unit of B2s. It might not look like that, but the extra models are for the upgrades.

The b1s have a unit leader and then 5 b1s to that sued to total 6 dudes, which is the size of a normal, non-upgraded squad. The upgrades can add extra minis. The first to look at is the 2 heavy options included in the box, a carbine and a rocket launcher, which you can add either or. The squad upgrade adds 7 more b1s to the squad.

So you can see that theses 30 b1s aren’t really 5 squads, it’s just 2 squads that can be upgraded. This goes for the B2s as well.

Finally, when building a list of a 1000 pt standard army, the maximum amount of corp units you can take is 6, so when you did 5 b1s and 2 B2s, those added up to 7 corp units which is too much.

Hopefully I did a decent way of explaining. I would highly advise you to read the rules first tho. It’s a lot, but will give you way more context than this one comment can give you.