If you don’t know about the conversion provision for a bridge financing, read this post on the conversion provision first. There are a few things that will be helpful to understand in relation to this question.
The most common numbers I see for the discount in a convertible note financing is between 15% to 25%. Therefore, if the venture capital investors agree to purchase the Series A Preferred Stock at $1 per share, the discount given to the angel investors when their notes convert is anywhere from $0.15 to $0.25. For example, with a 20% discount for the $500,000 investment, the angel investor would get a total of 625,000 shares of Series A Preferred Stock for his investment. His convertible note would convert to Series A Preferred Stock at $0.80 per share instead of the original $1.00 per share (i.e. $500,000 divided by $0.80 equals 625,000). This discount effectively gave the angel investor an additional 125,000 shares for coming in early and taking on the additional risk.