4 ram slots vs 2 - QNAP TS-1673AU-RP-16G, Thiết Bị Lưu Trữ NAS QNAP TS-1673AU-RP 16 Bay Chính Hãng slot mega 888

QNAP TS-1673AU-RP-16G 16-bay rackmount NAS, AMD Ryzen V1000 series V1500B 4C/8T 2.2GHz, 16GB DDR4 RAM (2 x UDIMM slots, max. 32GB), 2 x 2.5GbE LAN, optional 10GbE & M.2 NVMe/SATA SSD expansion via a PCIe, 2 x PCIe 3.0 x 4 slots, USB 3.2 Gen2 Type-C & Type-A, 2 x 550W PSUÂ

(The 2 RAM slots are what I currently use) So where are the other RAM slots? And if there is 2 more RAM slots, how do I utilize them?

ASUS AMD B450-STEEL LEGEND Motherboard: B450, AM4, AMD Ryzen 1st,2nd,3rd, DDR-4, 2133-3533MHz, 128GB, Dual, 4 Slots, Realtek ALC892 7.1, Realtek RTL8111H Gigabit, 2 Slots, 4 Slots, 2-Way CrossFireX, 6 Ports, Raid 0,1,10, 2 Slots, 4 Ports, 2 Ports, ATX