Power Adapter

From: Find the right power adapter and cable for your Mac notebook - Apple Support

"Power adapters for Mac notebooks are available in 29W, 30W, 45W, 60W, 61W, 85W, 87W, and 96W varieties. You should use the appropriate wattage power adapter for your Mac notebook. You can use a compatible higher wattage power adapter without issue, but it won't make your computer charge faster or operate differently. If you use a power adapter that is

lower in wattage than the adapter that came with your Mac, it won't provide enough power to your computer."

Hi,

There is no harm if you are using 30W Adapter for MacBook Pro 2016, just as you said it takes sometime longer to charging.