Fix for "zwanzig nach" x hours.

src/matrix/render_functions.cpp

@@ -164,11 +164,13 @@ String time_to_string(uint8_t hours, uint8_t minutes)
         message += "FUNF VOR ";
     }
 
-    // convert hours to 12h format
+    // increment hour when 25 minutes of an hour have passed
-    if (minutes >= 20)
+    if (minutes >= 25)
     {
         hours++;
     }
+
+    // convert hours to 12h format
     if (hours > 12) // 24h -> 12h, except 12h
     {
         hours -= 12;