Open Question: Waterproofing on Tents?

Hi, I'm looking to go camping in the summer and am looking for a tent. In most of the descriptions for them the waterproofing is described in mm and I cannot understand how this works? The tent I'm looking to get has 3000mm of waterproofing? Is this good? Thanks and I need an answer ASAP

Source: http://answers.yahoo.com/question/index?qid=20110525114820AAhjHYP "> http://answers.yahoo.com/question/index?qid=20110525114820AAhjHYP

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