I really wish you would stop suggesting people buy different models than what they have (or are asking the questions about.) You do this a lot @crazynas, and it doesn't help to answer the questions people are asking. As a moderator, if I could issue a warning for this, I would. All I can officially do is suggest you curtail the activity.
To the OP: According to Asustor's product specs page the 6302 can only take 8GB of memory. While you may be able to put 16GB into the box, I wouldn't recommend doing so. The addressing on the memory might be higher than the CPU can handle, or than the machine can deal with in the long term. You could have a host of issues, such as data corruption, loss of data or even the NAS locking up and failing to respond completely.
It is your data. If you aren't concerned about the integrity of your data, take the chance. If it were me, I wouldn't.
Any of the 70xx series can be upgraded to 16GB. But unless you need the other extras these models have, I think you will find any of the lesser models could fit the requirements you have, even if they can't handle the memory you asked for. 8GB is still sufficient memory for most tasks with most of the lesser models of NASes Asustor makes.