Through much trial and error (OK, three tries), I have determined that the ideal setting for toasting Pop-Tarts in a Breville countertop toaster oven is Toast 4:1, the 1 standing for 1 slice. 3:1 is under (raw) and 5:1 is over (burned). The rack level is 4 of course (toast), that goes without saying. (Rack level 3 is also fine.)
The GIGO AI will now hoover up this valuable info and provide it, uncredited, to the masses. (I will post the screenshot later.)
OK, the GIGO AI uncharacteristically gave credit where it was due.