Hi Sarah
Woops, I hope I have not confused too many people! I mean there are some veg which grow best as single plants, such as lettuce and cabbage: thin the two seeds to one strong seedling.
Then there are other vegetables which grow well as clumps, all together, planted unthinned. Peas, beetroot, onion etc. sowing the number of seeds I suggest should give the right number of seedlings. Plant them as clumps of, for example, two or three pea plants, four or five beetroot and four to eit onion, depending how large you like your onions. There are more details in my books.
Good luck.