Every business has a Service Industry Code, or SIC. This is a four-digit number that denotes the Merchant's industry type. For example, 5812 designates "Eating Places"; 8111 designates "Legal Services".

Some cards may have restrictions in place that limit the types of business at which they can be used -- for instance, an FSA card may only function at a pharmacy, or an EBT card might only be authorized at a grocery store. 

A decline 000062 indicates that the customer's card has a restriction of this type in place, which is preventing them from using that card at your type of business. Your customer will need to contact their bank for a further explanation and/or provide you with an alternate form of payment.

For more on SIC codes, the United States Occupational Safety & Health Administration has both a SIC search and structure breakdown.