progress callback: can be called more than once per sec

docs/libcurl/curl_easy_setopt.3

@@ -246,11 +246,11 @@ argument in the opensocket callback set with \fICURLOPT_OPENSOCKETFUNCTION\fP.
 Function pointer that should match the \fIcurl_progress_callback\fP prototype
 found in \fI<curl/curl.h>\fP. This function gets called by libcurl instead of
 its internal equivalent with a frequent interval during operation (roughly
-once per second) no matter if data is being transfered or not.  Unknown/unused
-argument values passed to the callback will be set to zero (like if you only
-download data, the upload size will remain 0). Returning a non-zero value from
-this callback will cause libcurl to abort the transfer and return
-\fICURLE_ABORTED_BY_CALLBACK\fP.
+once per second or sooner) no matter if data is being transfered or not.
+Unknown/unused argument values passed to the callback will be set to zero
+(like if you only download data, the upload size will remain 0). Returning a
+non-zero value from this callback will cause libcurl to abort the transfer and
+return \fICURLE_ABORTED_BY_CALLBACK\fP.
 
 If you transfer data with the multi interface, this function will not be
 called during periods of idleness unless you call the appropriate libcurl