I have some of the bulk crystals of sodium thiosulfate as well. I was doing a google search regarding how to dilute it and I happened upon the skeptical aquarist's website. I actually made a post there stating that 1g in 1L does not provide a 1% solution (which kuro pointed out). Still confused, I stumbled upon your post.
Following the directions outlined on the Kensfish website (and also the directions provided by GeToChKn), you will prepare a solution of 13% sodium thiosulfate. Quite different from the 32% that you obtained from the API website.
I have 3 possible thoughts regarding this discrepancy:
1) sodium thiosulfate is relatively safe, so the potential for error is small... better to overdose than underdose (I don't quite buy this one... why add extra chemicals if not needed)
2) the numbers may differ depending on what hydrous form of Na2S2O3 you are mixing (I'll gladly defer to kuro here
3) the amount that should be added to treat x gallons of water will be quite different depending on what concentration you are using. So obviously, you would need 2-3 times as much 13% solution to treat 10 gallons of water (compared to the 32% solution).
So given this, I'll ask... how much of the 32% are you adding (per volume)?
For the record, I have been mixing a 13% solution and have been adding 5 mL per 20 gallons of water changed. Fish are fine after more than a year of this.
Greetings of the season.