Is there a difference between PC4-21333 and PC4-21000 RAM for iMac 5K 27' 2019 I am trying to upgrade my iMac 2019 5K 27' to 64GB.

Per Apple specs, the RAM should be PC4-21333, but the only one I seem to be able to find on Amazon or macsales.com seems to be PC4-21000.

Is there an actual difference, or is it just a rounding choice?
Crucial.com shows it being PC4-21300 so I would ignore Amazon.

See https://www.crucial.com/usa/en/compatible-upgrade-for/Apple/imac-%28retina-5k%2C-27-inch-3*0ghz-intel-core-i5%2C-2019%29#MEMORYFilters