Updating RTC in Micrologix 1500 with MSG instruction

I need to update the RTC in a microligix 1500 PLC from a remote Micrologix 1500 PLC using a write MSG. I can ceate the write MSG and select the Data Table Address as RTC:0 but I cannot find any documentation that tells me what the Size in Elements wil be for this to work correctly. Does any one know what the element size should be?

Thanks for any Help or Suggestions.