Lecithin is well known in the male porn industry for boosting cum volume, sunflower is better than soy because of concerns regarding the phytoestrogens in soy possibly raising estrogen levels in men. Like other supplements its is poorly regulated and companies can claim almost anything without scientific proof.
As far as I am aware it doesn't do anything performance wise and I believe the dosage for increasing cum volume is around 3000mg or 3 of those pills. I doubt there have been any studies on humans so use at your own risk, and only occasionally
Google "lecithin ejaculate volume" for more anecdotal accounts but little science.
I could only locate one study on PubMed on a small sample of rabbits
http://www.ncbi.nlm.nih.gov/pubmed/22558930