[Question] What is the marginal impact of a small donation to an EA Fund?

I noticed that the EA Funds often disburse large amounts of money at a time. For example, all the grants paid out by the EA Long-Term Future Fund in September 2020 were worth $5,000 or more. As a more extreme example, the Global Health and Development Fund tends to give out more than $100,000 at a time. In either case, an additional small donation of $5 seems like it would have no effect on what the EA Fund does, whereas an additional $5 donation to the Against Malaria Foundation would directly purchase one net. What is the expected marginal impact of donating a small amount such as $5 to an EA Fund?