Rig means rig or GPU?

Hello community … I have a question regarding the pricing model.

It says that 1 rig with 4 workers are free and the account will be charged when adding another rig (3$ each in that case).

In my understanding a rig is a system which contains several gpus. A worker is one task mining with unlimited GPUs on one rig.

Does it mean that i can have 1 rig with 16 GPUs as a free user, or does rig mean GPU in that case?

Currently, i run one rig with 4 GPUs, but have another 3 GPUs which can be placed to the rig (same motherboard) …