I’m not sure what the extra digits indicate but I’ve come across this myself. ShipStation won’t accept it in the zip code field so I just put in the first five and then put the whole extended number on the address 2 line where an apt number would normally go.
The USPS postal code consists of several parts, used to identify increasingly smaller areas of postal delivery.
Zip Code. 5 digits used to identify the delivery post office (though not all of them actually contain a post office building any more).
Zip+4. A 9-digit Zip code; the original 5-digits representing a city, and 4 more digits. The first 2 of these are a postal delivery sector, and the last 2 are the postal segment. Sectors are things like a bank of post office boxes, or several blocks in a neighborhood. Segments are even more specific, like a block on one side of a street, or a certain floor in an apartment building.
there is also an additional 2-digit code, sometimes called Delivery Point, that identifies a specific address.
(Note that parts 2 & 3 can be changed by the post office, whenever the mail volume for an area changes, or even when they change their staffing assigned to the area.)
Most mail will have a barcode spray-printed along the bottom of the envelope that contains this 11-digit code. Bulk mail will usually come with this already printed with the address, either the 9-digit or the 11-digit version.
So what is meant by ‘full zip code’ varies, depending on the speaker. It’s not standardized.
I’ll bet that the Zip+4 is 00957-1926 and the street number is either 1, 101, 201, 301, etc.
the +4 zip code changes at a street intersection or whenever the hundreds digit changes. 499 Smith Lane has a different Zip+4 than the next door neighbor at 501 Smith Lane. Many bar codes have all 11 digits which makes every house unique. (I don’t know how they handle office buildings, some of which have their own 5-digit zip code.)