Turns out the type of bread and how long ago you bought it is extremely important when it comes to how hot you should set your toaster. When it comes to type, what they are made of is really important when it comes to getting the perfectly toasted piece: sweet bread and white bread generally heat up quickly, so you should use a lower setting, while heavier bread like rye bread will take more time to toast.
When it comes to when you bought that bread, you will find that even if you are toasting slices from the same loaf, you will need different settings for older bread. The more bread sits in your bread box it slowly starts to dry out which makes it easier to toast, so you need to lower the heat as opposed to a fresher slice of bread. Depending on how toasted you like your slices to be, you should take this into consideration.