Change FineSegmenter new parameter description

For more informations see #3268

algo/core/segment.h

@@ -359,7 +359,10 @@ class FineSegmenter : public Segmenter
    * Build a fineSegmenter based on KmerSegmentation
    * @param seq: An object read from a FASTA/FASTQ file
    * @param germline: germline used
-   * @param kmer_threshold: The number of the best k-mers for filtering.
+   * @param kmer_threshold: This threshold is used while filtering the V
+   *   BioReader in Germline. If this value is 0, every K-mer from getMultiResults
+   *   is used for the filtering. Otherwise if N > 0, the N best K-mers are used
+   *   for the filtering.
    * By default this parameter doesn't filter the germline.
    */
    FineSegmenter(Sequence seq, Germline *germline, Cost segment_cost,