What's the precision with SparkFun RTK Express Plus Kit in parks

Hi there, reading from SparkFun RTK Express Plus Kit description, it says the RTK Express Plus will have 300mm approximate accuracy out of the box and 14mm accuracy with RTCM correction. It also stated that with IMU combined with real-time GNSS tracking with advanced sensor fusion, it can work in tunnels, parking garages. So if I do survey in parks where some areas have clear view to the sky, but some areas have trees cover the sky, what will be the precision if we need to do survey in & out of these shade areas?

Precision will be lower in areas where the sky is obstructed. How much lower I can not say.