In the SYSTEM TYPE menu when linking the RX you can set the D/L (down link) or sampling rate in 0.1 millisecond intervals. Even using the 0.1 ms setting there is still going to be a lag in the vario. Even full scale varios have a slight lag and you need to work to not end up chasing the vario.

As far as I know you cannot alter the resolution of the setting in the vario itself. The range that is available is all you get.