These sums are notes (loans, debt). The money is either given as a check or wired. That is all. Just that simple. It is real money. Since it is a note, the investor gets zero equity (percentage, ownership). Rather, he gets [1] a compounded interest over time, in the case where the company has to repay, and [2] a percentage of the company "in the future".
Since startups go on to raise an A-round, investors who give startups loans (convertible debt), like to put a cap (maximum) on the amount of $ that may be raised in the future A-round. They do this because the higher the $ raised in an A-round and subsequent rounds, the more dilute the % the seed investor owns (if he does not follow-up). In this case, Yuri/SV Angels -- without fear of dilution -- are allowing the companies to "feel free to raise as huge a sum as they like/can in the future". There is, "at large", one main reason why a seed investor would do this: because he intends to and can participate in the future round. More basically, it is a branding statement that earns the entrepreneurs' trust or fondness.
The second provision is that of "discount". A discount simply answers the question: "How much % slack will you give me compared to your next round investor? i.e. How much cheaper "for me" will your stock be in your next round?". In this case, Yuri/SV Angels say they don't want any slack/discount.
What we don't know is if there is/was a liquidation preference (exit-clause or clause in case of a default). But that is another story.