Is amount of margin matter ?

The amount of margin can indeed matter in margin trading. Here are some key points to consider:

1. **Buying Power**: Margin allows you to leverage your capital, effectively multiplying your buying power. For instance, if you have $5,000 in your margin-approved brokerage account and you borrow an additional $5,000, you can buy up to $10,000 worth of marginable stock. This can amplify your potential returns, but also increases the risk you undertake.
2. **Risk and Losses**: The more margin you borrow, the more risk you assume. This is because the value of the collateral (your securities) must cover not only your initial investment but also the interest on the loan and any additional losses. If the securities' value drops significantly, you may need to deposit additional funds to cover the margin call or face liquidation of your position by the broker.
3. **Interest Costs**: Margin loans come with interest charges, which can add to your overall costs. The interest rate may vary depending on the brokerage firm and the type of security.
4. **Regulatory Requirements**: Margin trading is subject to regulatory requirements, such as the initial margin requirement set by Federal Reserve Board Regulation T, which is currently 50% of the total purchase amount. Brokers may have stricter requirements, and investors should ensure they meet these before engaging in margin trading.
5. **Broker Policies**: Each brokerage firm can define its own margin policies, including the minimum account equity required to use margin and the securities that are marginable. It's important to understand these policies before opening a margin account.

In conclusion, while margin can amplify your gains, it also significantly increases the potential for losses. The amount of margin you take should be aligned with your risk tolerance, investment strategy, and the potential for the security's value to change. It's crucial to consider these factors and not exceed your tolerance for risk when determining the amount of margin to borrow.