Multiple Monitors

Hi,

I have a laptop and two external monitors. I want to be able to view one thing on one of the external monitors and something different on the second monitor but can’t seem to do it. All I can seem to get is one screen on my laptop screen and the same screen on both external monitors. I have selected Extend these monitors. Should I be seeing 3 displays in settings or 2?
I am using a Microsoft surface pro. I have a a dock in laptop for hdmi port with hdmi cable connecting to hdmi spillter with two hdmi’s connecting into both monitors. Appreciate any help.