Hey there! That doesn’t sound like too much free storage. Not enough free storage and/or memory can start to cause troubles with the performance, as said before, I agree on having at least 10% storage space free, leaving room for data to sync or download, etc.
Heres a good article to follow if you haven’t seen it already:
How to free up storage space on your Mac:
https://support.apple.com/en-us/HT206996
That article is very useful, and also as said before, if your Mac’s HD doesn’t have enough storage for your needs, storing data on an external HD is a really good idea!
You can even store data like your Photos Library and your iTunes/Music Library, and make it default to your external HD. This way you can still enjoy all the same apps and data, despite having more data than your Mac supports, and won’t even be able to tell the difference, (As long as the external drive is connected).
If you cannot account for some of the data, it’s normal for some to be categorized as “Other” or “System”, say 10 - 30 GB. If more than that, then there may be data on there as well using storage, such as iTunes/iOS backups, lots of mail, or even diagnostics logs running that you don’t necessarily need running. (Such as in the Mail app, select Window on the top menu > Connection Doctor > There is a check box there for gathering mail logs, you can un check that to make it stop gathering the logs if you don’t need it, (Which is usually off by default).
Anyhow that’s just one example, there are many things you can do to control the storage being used on your Mac, so hope that helps!
