The amount of people you can invite to your workspace is based on the number of packs you purchase. Each pack provides 2 seats, with up to 10 seats for Pro Plan.
To put this into perspective:
If you purchase 1 pack, you will have 2 seats, and can invite 1 person to your team
If you purchase 5 packs, you will have 10 seats, and can invite 9 people to your team
If you purchase 6+ packs, you will also have 10 seats, and can invite 9 people to your team
If you need more than 10 seats, please email us at: enterprise@opus.pro