Minimum land requirement question

[Matthew Lessard]

I recently looked at a duplex in a mixed use zone. The first and seconed floor are used as residential rentals and the basement was used as an office space. I was interested in making the basement a studio apartment but when checking with the town they told me there is a minimum land requirement of 4 acres for a 3 family dwelling, yet the office is ok.This seems rediculous to me . Does this seem like a mistake or has anyone else ran into this?