Resolution problems with the second monitor.

I use to be a desktop user but my setup was pretty old and subpar. I sell all the hardware except for the monitor and bought a laptop Lenovo Legion Y540. When I use my laptop with the monitor using a HDMI to VGA adapter the monitor’s native resolution is 1024x 768, whereas the laptop’s native resolution is 1920x 1080. But when I used this monitor in my desktop setup its native resolution was 1920×1080. Is there something that I am missing? Now, what I have tried so far is I did a clean install of the display drivers. I have also tried updating the monitor drivers through device manager plenty of times.