You have to insert the proper numbers of the monitor you want to know how much bandwidth it will use.
This program was designed to help find out what kind of connection you need to be able to run your monitor.
Like 34BK95U-W (5120 x 2160 60hz) needs at least DisplayPort 1.3 to fully run it, becouse the program shows that it needs 18.4 Gbit/s, and DisplayPort 1.2 or older has 17.28 Gbit/s limit.