Number Posts under Label/Categories does not give a very good impression when you have too many post in one label/Categories and very less post in the other label/ Categories because less people will show interest in clicking them.
Here is an easy trick which you can do which will "Hide numbers being displayed under labels"
How to apply:
* Login to blogger -> Dashboard -> Layout -> html
* Check on "Expand Widget"
delete the code which you located and before you save your template just press preview if everything goes ok as you want ! then save your template!