Ok from right to left or closest to cpu
1st is pci-e x16 3.0 in one card config and x8 3.0 in 2 card config
2nd is pci-e 1x at 2.0
3rd is pci-e x16 slot at x8 3.0 in 2 card config4th is pci-e x16 slot at x4 2.0
---if you use this it could bottleneck your second card. I would measure and make sure you can use the 2nd slot and even if it barely fits and gets hot you can put a plastic spacer between them and a fan to push more air on them. If it doesn't fit in the 2nd slot I would recommend a pci-e riser, short preferably to avoid interference.
Here is the manufactures specs
Warning: Spoiler! (Click to show)
1 x PCI Express x16 slot, running at x16 (PCIEX16)
* For optimum performance, if only one PCI Express graphics card is to be installed, be sure to install it in the PCIEX16 slot.
1 x PCI Express x16 slot, running at x8 (PCIEX8)
(The PCIEX16 and PCIEX8 slots conform to PCI Express 3.0 standard.)
* Whether PCI Express 3.0 is supported depends on CPU and graphics card compatibility.
* The PCIEX8 slot shares bandwidth with the PCIEX16 slot. When the PCIEX8 slot is populated, the PCIEX16 slot will operate at up to x8 mode.
1 x PCI Express x16 slot, running at x4 (PCIEX4)
1 x PCI Express x1 slot
(The PCIEX4 and PCIEX1 slots conform to PCI Express 2.0 standard.)