It means someone spun a wheel with numbers on it twice - 10 came up once and 20 the other time!

Generally, it means until you can see a shoot coming through the soil. But there are so many variables: soil temp, air temp, soil moisture, deepness you plant the seed, how old the seed is, the temperatures they have been stored at.... you get the idea!

Mike

Mike has it right ~ it's from sowing to emergence from the soil. He also has it very right that there are variables. I have tomato seeds right now in the greenhouse that were sown at the same time ~ new seeds have been up for two weeks and old seeds are just now sprouting. And compare mine to my neighbor's ~ sown the same date, his in his heated greenhouse have been up for quite a while before mine in my unheated g-house.

If you get into the more obscure type plants with complex germination patterns, you will find references to germination where they are talking about root emergence only. Some plants like Trillium and Lilies will send out a root first, then they need a cold period before they will make a green shoot.

Teeeeeeechnically speaking there is germination, following that is emergence. Germination is a physiological process that occurs prior to emergence from the seed coat. But who cares! From my observations, seed packs are refering to emergence and yep, there are variables.