The rate tied to inflation is set every 6 months (May 1 and November 1), and when you buy a bond, the rate holds for 6 months. So if you bought on April 25, then in October you would get approximately 3.6% of the value of the bonds you bought, and the rate would reset to the current 6 month period, which is expected to be somewhere around 9% when they announce it soon.
You can cash in the bonds after either a year or 15 months (I don't remember for sure), but if you cash them in less than 5 years, you lose 3 months of interest. I'm guessing they don't give you money if you cancel when the rate is negative which can happen.
