Sorry for the late response, but this…
seems very low. I suspect that while using iSCSI won’t lead to any immediate problems, it is likely causing enough latency for your node to miss out on receiving quite a few pieces.
I’m not entirely sure why you chose this setup. Since the Synology machine would be perfectly capable of running the node itself. In fact I have 4 nodes running on a Synology myself on different internal and external drives.
For reference you can use the Realistic earnings estimator
Currently it estimates you should have been able to collect around 3.5TB after 10 months. If you don’t have a lot more space to share, it may not matter anymore, but since you mentioned you have about 20TB, you would really benefit from optimizing your setup, As anything that leads to less ingress, will also impact the total amount of storage your node will theoretically get.