To be fair their calculation also involves multiplying by the carefully chosen factors of 4 and 0.25. It’s a macroeconomics thing you probably wouldn’t understand. https://ustr.gov/issue-areas/reciprocal-tariff-calculations

The recent experience with U.S. tariffs on China has demonstrated that tariff passthrough to retail prices was low (Cavallo et al, 2021).

This “Cavallo” reference isn’t actually listed in their citations (gee I wonder why) but appears to be Tariff Pass-Through at the Border and at the Store: Evidence from US Trade Policy (link).

Meanwhile Cavallo et al 2021:

Chinese exporters did not lower their dollar prices by much, despite the recent appreciation of the dollar. By contrast, US exporters significantly lowered prices affected by foreign retaliatory tariffs. In US stores, the price impact is more limited, suggesting that retail margins have fallen. […] Our results imply that, so far, the tariffs’ incidence has fallen in large part on US firms.

Amazing. The government’s official position is that tariffs are OK because both US exporters and importers get less money.