Although the unit put out initially low numbers of only 40 MB/s with a single client, it managed to maintain a good overall performance of up to 85 MB/s with four and five clients, which is pretty good for a home NAS that uses a comparatively weak CPU; that is, to high-end NAS servers.
Performance with multiple clients was fine, but the CPU struggled to keep up, and everything would probably slow down to a crawl if you were to run other services at the same time. But do not forget that this is a home NAS, so it will most likely never face a scenario where multiple clients ask for huge volumes of data at the same time.