A balcony should be a place to relax, not a swimming pool after every rain. A wrong slope is a major defect that builders often ignore.
The Danger
If water stands on your balcony, it will eventually find its way under the tiles and into your living room walls through capillary action.
How to Check
Pour a liter of water at the farthest corner from the drain. It should flow smoothly to the outlet without leaving puddles. If it doesn't, the builder must re-tile.