You’ve managed to assign the group which forms the number “2” to Layer 2, but you’ve also assigned the primitive geometry (faces and edges) that actually form the number “2” to Layer 1.
So when you turn off visibility of Layer 1, you also turned off visibility of all the geometry contained in the number “2”. So the grouping that organizes the number “2” is visible, but the actual geometry is not!
I made the same sort of mistake when I was a noob, so don’t feel bad about this.
The general rule of thumb is: Keep all primitive geometry on Layer 0! And always keep Layer 0 visible and the active drawing layer. The only things that should be assigned to other layers are the containers (groups and components) that serve to associate a set of primitive geometry together. Containing geometry in groups and components also prevents the geometry from interacting with geometry in other containers or uncontained (“loose”) geometry.
There are, of course, exceptions. You can do some fancy control of what is visible if you have nested containers with the outer containers assigned to different layers than the inner containers. Many people also put dimensions, text, and layout lines in their own layers - but none of these entities are considered to be “primitive” or “raw” geometry. I actually hesitated before outlining these exceptions (there are more) because, as a newcomer, you’re far better off adhering fanatically to the general rule - and learn about how the exceptions can be useful only if and when you encounter a modeling situation in which breaking the general rule makes sense.
To “fix” your model, double click on the letter “2” to open for editing, then “Select All”, right click for the context options and select “Entity Info”. In the resulting dialog, pull down arrow to the right of “Layer1” and select “Layer0”.
You should do the same for each of your other letters - that is: reassign the geometry to Layer0 while leaving the container (group) in your preferred layer.