You can show only one decimal place if you select the field while in layout mode and use the numeric data formatting options at the bottom of the inspector's tab to specify only a single decimal place. This will result in a value of 10 displaying as 10.0.
Or you can round the actual value computed to a single decimal place using the round function:
Round ( Your calculation expression goes here ; 1 ) will round the value computed to one decimal place. A value of 10 will still display as 10, but a value of 3.1415 will display as 3.1.
Thansk PhilMod, I knew it would be simple the Data forrmating tab was collaspsed I hadn't even noticed it tucked away at the bottom, I just tried its made the figures %. Something I have done I am sure so will look with fresh eyes and head in the morning