When this story came out last month that is what was being reported, the 173 was all of the RWD cybertrucks sold.

However it only effects certain build dates:

Some reports have suggested that the recall number of 173 reveals a staggeringly low number of RWD Cybertrucks made, but Tucker says this isn't the case. The recall applies to trucks built on certain dates using a specific shipment of lug nuts and grease, and cars with 18-inch wheels produced on certain dates. He says it's a “subset of a subset” of Cybertrucks.

https://www.wired.com/story/the-latest-tesla-recall-wheels-may-fall-off-cybertrucks/