As both Andrea and Terri correctly stated, Trulia pulls the information straight from the MLS listing, so if there is a problem it likely is generated from 1) the listing on the MLS or 2) the county records. When we input any listing into the MLS, the system automatically generates the square footage for the home and the size of the lot from the County's records, based on the Assessor's Parcel Number or APN.
I see, thankfully, that the listing on Trulia now states that the lot size is 5980, so this now appears on the corrected version of your posting.
Area Pro Realty-People's Choice
Please note that it appears your agent has listed the lot as you stated, but the "Public Report" has it listed differently. I suggest you talk with your agent to determine if the county records has an error or the website.
Have an amazing day!