Crying for help -- size of the lot bought isn't right!!

[Rebecca Chen]

This is my first post. I am a completely newbie here. The reason for my first post here is that I have a big problem. I bought a piece of residential lot in harris county auction. The land area listed in appraisal district (HCAD) is 3000 sqft. 

When I go into the online county map (Key Map) to look for this lot based the legal description, I did the calculation by myself based on the dimensions shows around the lot. I came out with the lot area of 2000 SQFT. The reason in this giant difference is because this lot has one end as a "triangle", it seems that the 3000 SQFT is calculated base on the triangle is a full rectangle. 

Am I in big trouble? This is a 1/3 reduction in lot size!! How can I verify which information is correct? To whom should I seek for help to to get more information around this lot? 

Any help is appreciated!