4 x 4 slot ✓ AMD Socket AM4 Chipset

Your assumption is correct This would be a slot with only four PCIe lanes connected, but it can fit a 16-lane card This is pretty common,4 x 4 slot,the PCIe slot There are essentially four types of PCIe slots differentiated by their lane count

To make full use of i7 performance, Nuvo-4000 comes with 4 PCIPCIe expansion slots There are two configurations, x16x4 PCIe slots + 2 PCI slots , 4 x 4 slot,- 4 x DDR4 DIMM Slots - AMD Ryzen series CPUs support DDR4 4666+( - 1 x PCI Express x16 Slot (x4 )*

4 x 4 slot,4X4 Designed with AMD Ryzen™ Embedded, ASRock Industrial's 4X4 boards offer rich IO and flexible expansion slots for embedded applications