The limits are identical across Classic, Horizon, and Zenith.
There is no scaling plan. Your full limit is available on your first trade and does not change as your balance grows.
How the limit is counted
The limit applies to everything you hold at once, across all open positions, not per trade and not per instrument. Two ES and two NQ on a $50K account is four contracts, which is your ceiling.
Ten micros equal one mini. On a $50K account you can hold 4 minis, or 40 micros, or any mix that adds up: 2 minis plus 20 micros is exactly at the limit.
If you exceed it
The limit is enforced on the platform side, so an order beyond it is rejected.
