The shift from 10,000 to 500 is prompted by a discovery on Rococo. When a parachain placed a batch call for approximately 5,000 orders in a single block, coupled with Rococo's abundance of on-demand cores at the time, block import times slowed significantly, as evident in [the reported issue](https://github.com/paritytech/polkadot-sdk/issues/3051). To address this temporarily, we're restricting the total number of orders by adjusting the configuration through `configuration.setOnDemandMaxQueueSize` to a smaller value, and for the initial launch, 500 is a safe limit. Once a more permanent solution is in place, the maximum orders can be revisited.

Note that the OnDemandQueue stores orders made on the relay chain which have yet to be assigned a core. The maximum size represented by `onDemandMaxQueueSize` is the absolute maximum that this storage entry can be. It is further bounded via an optimal price controller, which is currently set to try and maintain 0-25% of the max capacity without increasing the price of an order.

See [`Pallet::dispatch_whitelisted_call_with_preimage`].

- **Problem Statement:** Adjusting the configuration on Rococo due to slow block import times caused by a large batch call for 5,000 orders.
- **Significance:** Rococo's on-demand cores abundance led to significant delays in block import times, prompting the need for a temporary solution.
- **Proposed Solution:** Temporarily limiting the total number of orders to 500 by adjusting the configuration through `configuration.setOnDemandMaxQueueSize`.
- **Expected Outcomes:** Improved block import times and smoother processing of orders on Rococo with the reduced limit of 500 orders.

#345 Setting setOnDemandQueueMaxSize to 500