Nothing to worry about... it's called the trub. It contains alot more than just hops, such as proteins and other particles that are created during the brewing process. You can use a sanitized turkey baster to retrieve enough wort for a OG reading... however, since it's extract... as long as you hit your target water amounts, it should be close to what is specified in the instructions and I wouldn't worry about it. Now, start planning your next brew and leave that one alone for at least three weeks.
