Motherboard installation help

Jun 22, 2018
Howdy! I'm brand new to PC building and I just have some concerns about whether I have my motherboard mounted safely in regards to its number of screws and the case standoffs. I have an NZXT S340 case with an MSI Z370-A Pro motherboard. The case comes with 9 equally sized standoffs preinstalled (8 have their own designated letter in the diagram, 1 is centered on the case with it its own special letter). The mobo has the same number of screw holes as the case has standoffs, 9.

Is the one specially designated standoff just for me to like center the board? The case instructions have a legend for positioning your motherboard depending on its size. A for ATX, U for Micro ATX, and I for ITX, with some of these slots being shared with one or more types. My board is an ATX, so do I ONLY need to make sure there is a standoff in areas marked with the letter A and remove any remaining standoffs with the standoff wrench? If so, this leaves me with 9 motherboard screws and 7 standoffs. MATH! I just really don't want to fry my poor motherboard.

Here's a diagram I drew of the one from the case's manual:

Thank you!
Included is an extra standoff and a socket to remove the preinstalled ones if you do not plan to use an ATX motherboard, as that is how it is setup from the factory.

7 standoffs is the wrong placement for ATX motherboard.