diff --git a/docs/libcurl/opts/CURLINFO_CONTENT_LENGTH_UPLOAD_T.md b/docs/libcurl/opts/CURLINFO_CONTENT_LENGTH_UPLOAD_T.md
index 219481f43d..7b5d058521 100644
--- a/docs/libcurl/opts/CURLINFO_CONTENT_LENGTH_UPLOAD_T.md
+++ b/docs/libcurl/opts/CURLINFO_CONTENT_LENGTH_UPLOAD_T.md
@@ -31,6 +31,11 @@ CURLcode curl_easy_getinfo(CURL *handle, CURLINFO_CONTENT_LENGTH_UPLOAD_T,
 Pass a pointer to a *curl_off_t* to receive the specified size of the
 upload. Stores -1 if the size is not known.
 
+This is the size set by the client prior to the transfer start. The expected
+upload amount. Compare this with CURLINFO_SIZE_UPLOAD_T(3), which is the
+amount of data that was actually uploaded in the end. In many cases those two
+numbers are identical.
+
 # %PROTOCOLS%
 
 # EXAMPLE