i was also considering this product. haven't purchased yet, but here's some investigation:
jasco site for the product:
https://byjasco.com/ultrapro-z-wave-in- ... wire-white. let's assume model is 39351
z-wave alliance product page:
https://products.z-wavealliance.org/pro ... quencyId=2 configuration capabilities page linked from above page.
https://products.z-wavealliance.org/pro ... 31/configsfrom that page, parameter 6 appears to be a boolean (0 or 1) where 0 means the light dims "quickly" and 1 means it dims "slowly".
however, i don't see any actual ability to set the ramp rate beyond that - e.g. for other brands, i've found you can directly set a number of steps and/or an amount of time between steps giving you finer-grained control, but that does not appear to be the case with this brand.
if i chose the wrong specific model, you can probably still re-trace the same steps i've shown above to find the specifics of your model.