With a 40% achievement in the Test Planning process area, the rating would be "Partly achieved." According to TMMi, a process area is rated "Partly achieved" when the percentage of achievement is between 15% and 50%. This indicates that some practices have been implemented, but significant improvement is still required to meet the full requirements of the process area.
Reference:
"Achievement levels like 'Partly achieved' correspond to percentage ranges, with 40% falling under the 'Partly achieved' category".