Man pages matching name gnutls_record_set_max_size in section 3:

gnutls_record_set_max_size.3.en	debian 10 / gnutls-doc
gnutls_record_set_max_size.3.en	debian 11 / gnutls-doc
gnutls_record_set_max_size.3.en	debian 12 / gnutls-doc