Sometimes, a connector will have extra leads or pins that don’t match up with the described number of pins. Typically these are support or mounting leads, which make no electrical contact but are added to provide more stability or a stronger support for mounting the connector to a PCB.
However, sometimes the supports are not so obviously different from the electrical contacts.
For example, H11632DKR-ND from Hirose is described as having 80 pins, but has 84 leads connected to the board.
This seems odd at first glance, but a quick look at the manufacturer’s drawing (available on the product page, and here: Drawing Download) shows that the leads at each corner are no contact, purely for mounting purposes. They describe them as “Metal Hold Down” contacts.
In most cases, the manufacturer data sheet or other available documentation will verify whether the the discrepancy in what you’re seeing and the part as described is accounted for.