Hello! Thanks for your support.
If you keep watching it you will see what happened. It's just me pressing CTRL+M (cmd+m if you are on mac I believe) to use the auto mapping tool. The thing is that the standard auto tile for the Tiled only supports tiles such as terrains which are 1 tile tall. However, for walls with 2 tiles tall or more, we have to create all the rules by ourselves. I've already done it for you, you just need to pick the brush, draw and then use auto mapping tool (press CTRL+M or go to map then automapping at 2:20). If you followed exactly what I did and created a new layer with the same name, then what happened is this: when you create a rule this rule is linked to a layer, if you have more than 1 layer with the same name then only the first one (from bottom to top) will be picked. If you are wondering why I created another layer, there's nothing special to it, I just needed an empty layer to redraw the platform and showcase it in the video.
Important notice: don't use the 'Automap while drawing'. You have to draw first then press ctrl+m. If you want to redraw it, do what I did in the video and delete the part you want to redraw and then use the brush again.