only implimented min/max precision & step.
at the moment there is no way to edit these other then via python
example of setting UI limits...
>>> C.object['foo'] = 0.5
>>> C.object['_RNA_UI'] = {'foo': {'step': 0.5, 'soft_max': 10.0, 'soft_min': 0.0, 'precision': 2, 'description': 'Some setting'}}
Also fixed typo's: precission -> precision