Editions around this time suddenly have a weird qualification:

Twenty-ninth edition in this format: November 2019, fourth reprint: November 2020

Revised and corrected edition.

I interpret this is as the 4th print of this ISBN with the HP1-SPA-iv-V71 text. For this ISBN, that would make it the 32rd print. (1:29, 2:30, 3:31, 4:32).