We're doing all of the tier management by hand so if we've confirmed that we've moved you to a new tier in a Kickstarter message then you are in fact moved. Please fill out the survey you've been given as we've probably already asked you any other pertinent information directly (such as what prints you would like, etc.) Feel free to write us with any questions about having moved tiers.
The size charts for the shirts can be found here for MEN: http://www.americanapparel.net/sizing/default.asp?chart=mu.shirts and here for WOMEN: http://www.americanapparel.net/sizing/default.asp?chart=womens.shirts .
Don't see the answer to your question? Ask the project creator directly.