When you park the actual rate is an intermediate rate calculated from the 2 nearest rates. So if the rate for 1 year is 5% and the rate for 2 years is 7%, when you park for 1.5 year your annual rate will be 6%.
Here we have only one rate so this calculation doesn’t work and it returns zero. Actually it works if you park for exactly 8192 blocks (about 5.7 days). It’s very hard to do that with the GUI, but it works with the park RPC command because you must provide a number of blocks.
Jordan suggested we change that behavior so that if you park for 4.2 days (i.e. half way between 5.7 days and the next possible shorter duration: 2.8 days) then the actual rate would be 0.05%.
I’m wondering whether people would instead expect the rate to be flat for the entire duration: 0% from 0 to 5.7 days, 0.1% from 5.7 to 11.4 days, and 0% for any longer duration.