In general, a withe Number (Mostly Above The Signal) Multiplied by Ten Means Maximum Speed A Yellow Number (Mostly Below the Signal) Multiplied by Ten Means Maximum Speed at the Next (Main) Signal A Signal only showing a Yellow and a Green Light always mean go with 40 Kph
When you want to dig deeper into German signaling - especially when you start using PZB, check out http://sh1.org/eisenbahn/