Check out the FAQ's on that forum....it will give you all of the answers.
You are not actually supposed to ask for seeds....it is trade only unless the SASE is offered to you. If you want clarification on how many seeds are in each individual trade, ask them and tell them what you are sending. Communication is everything.

About two dozen is the usual amount for a trade. You can contact a trader through email rather than post a request for a SASE, which is tabu on the exchanges, because it invites too many greedy people. People will post if they have seeds to share, epsecially in Autumn and Winter after everyone has harvested seeds from their gardens. They trade and then SASE away what they don't need.

I made a collection of seed trading FAQs for the Winter Sowing Forum--we have an exchange. I'll paste in the link for you. The FAQs for seed trading are about 2/3s down the list.

Here is a link that might be useful: WS FAQs--seed trading FAQs are about 2/3s down the list

WebKat an Trudi,

Thanks so much for your help. The FAQ's were great and answered all my questions! Don't know why I didn't see the link originally! And Trudi, thanks for all your hard working putting all the information together for folks like me! It's great.