Man pages matching name curlmopt_content_length_penalty_size in section 3:

CURLMOPT_CONTENT_LENGTH_PENALTY_SIZE.3.en	debian 10 / libcurl4-doc
CURLMOPT_CONTENT_LENGTH_PENALTY_SIZE.3.en	debian 11 / libcurl4-doc
CURLMOPT_CONTENT_LENGTH_PENALTY_SIZE.3.en	debian 12 / libcurl4-doc