Note, this does not convert a 2 port connector to 4 devices - it's intended for situations where you have a USB internal device (such as a fan controller or liquid cooler controller) that takes up the 9pin connection but only uses one port (that is, with 4 or 5 wires).
This cable allows you to use both ports.
However, use it with great care - it's not a hub and you can't have two USB devices on one side. Check the cables on your devices and if they both use the top row, make sure to offset one plug to the bottom row so that they have a line each.
If you don't understand USB pin-outs then don't chance it as used wrongly it's possible to cause damage to your devices.
See this article for pin-out info - https://superuser.com/questions/619839/do-i-need-to-use-the-extra-ground-pin-10-in-an-internal-usb-header