The lower or below ground square footage if finished (HVAC, electric, wall covering, flooring, etc.)will be counted in the total heated square footage of the home, but in most cases it will not hold the value as upper level(s) or above ground square footage upon appraisal time. You will find that appraisers may or may not give the below ground/finished basement the value one would expect as the upper finished level(s). Keep in mind that if the below ground/basement meets or exceeds the upper level(s) finished product (ceiling height, flooring, moldings, etc.) you will be more likely to get a favorable value.
Hope this will help in answering your questions and or concerns you may have.