No values for dpt 13.001

Dear all

I try to represent a counter (dpt 13.001) in openhab. However I only get zeros in sitemap (although in log file the 4 byte value shows something different to zero).

The thing is:

Thing device  Zaehler [ address="1.1.21", fetch=false, pingInterval=300, readInterval=0 ] 
{
Type number         : Wasserzaehler                             [ ga="13.001:<8/4/0" ]
}

The item is:

Number          Wasserzaehler                                    { channel="knx:device:bridge:Zaehler:Wasserzaehler" }

The log file shows:

21:42:54.692 [TRACE] [knx.internal.client.AbstractKNXClient] - Received a Group Write telegram from '1.1.21' to '8/4/0' with value '[0, 0, 1, 74]'
21:42:54.695 [DEBUG] [x.internal.handler.DeviceThingHandler] - onGroupWrite Thing 'knx:device:bridge:Zaehler' received a GroupValueWrite telegram from '1.1.21' for destination '8/4/0'
21:42:54.699 [TRACE] [x.internal.handler.DeviceThingHandler] - onGroupWrite Thing 'knx:device:bridge:Zaehler' processes a GroupValueWrite telegram for destination '8/4/0' for channel 'knx:device:bridge:Zaehler:Wasserzaehler'
21:42:54.703 [TRACE] [ng.knx.internal.dpt.KNXCoreTypeMapper] - toType datapoint DPT = 9.001

Anybody an idea what the problem could be? Any help would be highly appreciated

Best regards
Rolf