Change the breaker to 30A. The instructions are part of the Listing, and the NEC requires following them.
Sometimes you have to figure out how to comply with multiple code sections, here at least 3 have to be considered. Section 422 deals with appliances:
NEC 422.11(E) Single Non-Motor-Operated Appliance. If the branch circuit supplies a single non-motor-operated appliance, the rating of
overcurrent protection shall comply with the following:
(3)Not exceed 150 percent of the appliance rated current if the
overcurrent protection rating is not marked and the appliance is rated
over 13.3 amperes. Where 150 percent of the appliance rating does not
correspond to a standard overcurrent device ampere rating, the next
higher standard rating shall be permitted.
You also have to go back to the beginning, section 110 Rules for Electrical Installations:
110.3(B) Installation and Use. Equipment that is listed, labeled, or both shall be installed and used in accordance with any
instructions included in the listing or labeling.
UL/CSA/ETL Listings require installing and using as instructed in any enclosed instructions. Page 11 of the instructions shows a table, says 30A for 120/240v ranges. 30A is less than the maximum of Section 422, so only a 30A breaker complies with both Sections 422 and 110.
The receptacle can remain a 50A:
NEC 210.23(B)(1) Single Receptacle on an Individual Branch Circuit. A single receptacle installed on an individual branch
circuit shall have an ampere rating not less than that of the branch
A 50A receptacle is not less than 30A, so satisfies the reqirement when it is a single receptacle on a branch circuit.
There is some confusion about the receptacle rating, eyes are drawn to an irrelevant table, 210.23(B)(3). The table for years was titled "Receptacle Ratings for Various Size Circuits", it shows a 30A breaker only allows 30 receptacles. But the table doesn't apply! Section 210.23(B)(3) only applies to circuits with multiple outlets. The 2023 edition of the NEC makes this more clear, the name on the associated table has been changed to clarify to now read "Receptacle Ratings for Circuits Serving More Than One Receptacle or Receptacle Outlet".