1 x pcie 4 0 x16 slot ✓ PCI-E x16 1 to 4 Expansion Card Gen3 Split Card PCIe

1 x pcie 4 0 x16 slot 1 x PCIe x16 slot I understand the first bullet point, but Why does a PCIe slot which has only 4 lanes physically has 16-slot size?

Gigabytes per second over a x16 PCI Express lane for graphics controllers PCI-Express 1x Connector Pin-Out Pin Side B Connector

SATA Ports : 8x SATA 6Gbps ports PCI : 1x PCIe x16 slot 1x PCIe x16 slot 1x PCIe x1 slot PCI-EX : 1x Gen5 x4 128Gbps slot 4x Gen4 x4

I tried to move my VGA to the second PCIe 16x slot on the motherboard and found that my VGA can run on PCIe 16x and indeed

SATA Ports : 8x SATA 6Gbps ports PCI : 1x PCIe x16 slot 1x PCIe x16 slot 1x PCIe x1 slot PCI-EX : 1x Gen5 x4 128Gbps slot 4x Gen4 x4

PCIe runs at 2GBs per lane So A PCIe x16 slot with x4 lanes supports bandwidths up to 8GBs, and a PCIe x16 slot with x1 lane