Sat = 23% means that the share of satellite data when interpolating is 23%, the rest corresponds to station data, interpolated from nearby stations. Meteonorm does use a mixture of satellite and station data. The further one is from the stations the greater the weight of satellite data.
For more information about meteonorm, please also look at their documentation. For example their handbook's chapter 7.2 describes the interpolation in more details https://meteonorm.com/assets/downloads/mn80_theory.pdf