AMP uses the same Industry Standard SPAN margin calculations for carried "Open Positions".
Every spread starts as individual leg/contract until the risk systems recognize the spread and then adjust the required margin used intra-day to the spread margin requirement vs the individual leg/contract.
For example, if you buy 1 ES contract - the required day trade margin is $400 and you sell 1 NQ contract - the required day trade margin is $500. The total initial intraday margin to initiate both legs of this spread is $900. Once both legs are filled, the risk system will recognize the spread and reduce the margin used from $900 down to the exchange spread margin requirement - give the account more buying power to initiate any future trades.
This is confirmed how CQG, Rithmic and TT pre-trade risk systems work.
If you have any questions or would like to confirm margin requirements - please do not hesitate to email
trading@ampclearing.com