Jessie, it's great that you will be in the swap! As long as your description of your pkt size is pretty close, that's a fine amount to offer. Someone who really wants to try out a variety will welcome enough seeds to get a few plants. Someone who wants to scatter-sow a block and eat them all summer will pick out larger packets.
I think that "20 seeds" is a minimum for things that are not rare or expensive. That might work for perennials where you only need a few plants, and then you have as many as you want forever. I think that if germination is low or unknown, more than 20 seeds is kind. For hand-pollinated big seeds like daylilly seeds, or5 hard-to-collect Salvia seeds, small numbers might be appropriate.
And for common, annual, edible crops, I try to include at least enough seeds that they will get enough plants to really know how they like them, even if germination is low. What would that be, 5-10 row feet?
Mostly, I divide up whatever amount I have and try to get 5-10+ pkts out of it. But I learned from past swaps that if my pkts "look small" to my eyes, I'm not happy. Maybe the person receiving it won't be happy either. That must not be!
Now I figure that I would rather give away fewer packets, big enough to make me feel proud. The unusual and expensive hybrids are exceptions, because it might take several commercial packets just to add up to 1/8th tsp! Then I put "SMALL PACKET" in the description, and figure that someone who picks it, must really want to test that exact variety, even if they didn't get enough seeds for succession planting.
When I make up trade packets, the size depends on the size of the seeds, age, how many seeds I have, or how much they cost me. When I get a bulk pack at a great price, like a whole OUNCE of small Brassica seeds, or inexpensive OP seeds, I'll put 1/8 tsp or more.
If they are a pricy Brassica hybrid and I only got a small pinch myself, the packet will be 1/16th tsp ~~ 125 seeds
Lettuce was mostly 1/4 tsp to 1 tsp, except for some varieties that were more expensive - 1/16th tsp or 1/8 tsp.
I only bought small, single pkts of Frank Morton's "Flashy" series lettuce because they were newish and pricey that year, so I made just a few pkts of 30-50 seeds each: "scant 1/32 tsp ~~ 30 seeds SMALL PKT". I see that the online price of those new varieties is already dropping!
For chard or spinach (big cheap OP seeds), I made packets of 1/2 or 1 teaspoon. One kind of chard was older and I had a lot, so I made pkts of 1.5 tsp >150 seeds >2.5 gram. When my seeds get a few years old, I would much rather several people had enough of them to sow lots and not worry, rather than just let them keep getting older in a tub inside a box!
I just LOVE saving, collecting trading seeds. You meet the nicest people and a HUGE variety of seeds, without paying an arm, a leg and a kidney for S&H.
In my case I have an extra reason to feel good about seed trading. I make some other people feel LESS crazy!
