Nextcloud and SMB external storage disk size on sync

I’m using NextCloud with mounted external storage SMB and sync client on Windows. All data from my PC are synchronized/synchronaizing using NextCloud with the share. It’s working, but I figure out that size of folder of nextcloud data is dynamicly growing. Why its happening when all data are on the share? I see that from time to time size of used space is getting shrinked but afterwards still growing. I.E now is 7GB goes to 10GB and then again 7GB. Is there any option to make a quota on this folder or to limit make a limitation of amout of files what can be synchronized in the same time, or make some cleaning operation on this folder?