2,6ghz? dual core? quad core? 8 xeon cpu with 24 core each? 6gb ram are low and a bad setting, because for build a 6gb computer you will need 2gb and 4gb sticks, no dual channel .. now the minimum standard is 8gb, 16gb the ideal for most players. And if is old Intel cpu with the patch for meltdown and spectre.. the cpu become a brick.
In this game, like all games with similar structure (no limits for building, units, bots..), the minimum system requirements is closely related to the complexity of the simulation. A colony with 50'000 settlers, 400 bots and 10'000 building is different from a colony with 2'000'000 settlers, 2000 bots and 100'000 building.
In any case, why you need 4000 robots?
In end game style, all resource come from building, not for harvesting. In my LIS colony, i have only few hundreds bots, just for create structures.