When the app tries to buy a stock, it will calculate the position size based on your risk factors. In the event that the resulting position size calculated exceeds your buying power, the app needs to know what to do. The options are either:
Do nothing and error
Buy the max amount it can
Need to be careful with the latter option, as it won't be able to simply buy the full amount in the account, otherwise the order will be rejected due to no money to pay for the fees
When the app tries to buy a stock, it will calculate the position size based on your risk factors. In the event that the resulting position size calculated exceeds your buying power, the app needs to know what to do. The options are either:
Need to be careful with the latter option, as it won't be able to simply buy the full amount in the account, otherwise the order will be rejected due to no money to pay for the fees