Look at the text “replace with”. At the left, you see manually created GUI, at the right - Gui created with script. The only diffirence that should be here is text color diffirence, but as you can notice, right text much bigger than left one. You can notice same thing with “Material settings” text.
But the most interesting thing that here EVERY property exept text color is the same.
Can someone tell me, why I receive so strange result with RichText usage?
I’ve tested your code, and nothing in it seems to be off. It works as expected for me, so maybe it is just on you? Maybe check the properties of the code-generated TextLabel and see if the TextSize property is all right?