Let me give a comparison with something commonly done, the Sun. When something is called "As powerful as the Sun" or "It's 20 times more powerful to the Sun" or even "Can create a sun in the palm of their hand" we don't scale it to the Sun directly, we look at what property it's more likely being compared to the Sun and reproduce it with the scale that is being shown.
That could mean giving the temperature of the Sun to the miniature sun, or comparing it to the energy released by the sun, etc. If we are indicated what allows the comparison, that is what we use (For example, if something is said to produce 20x the energy the Sun produces, we multiply the luminosity of the Sun by 20 and use that value).
That is, they can compare it to cosmic Gamma Ray Bursts, if they don't give something more to it than saying "It has this frequency that is the same as the ones from Gamma Ray Bursts", there's no need to actually scale it to anything other than that frequency. If it's a gamma ray burst, what defines it is the photons being in the gamma ray frequency/wavelength, which we have confirmed to be the case.
I did see the gif that said "You only see these kinds of spikes from pulsars. Supermassive black holes from outer space.", but as I said, if we don't have anything more to it other than the frequency to compare, there's nothing more we can do about it. Like, it's reading something and that reading is on the level that can only be found on pulsars, but what is being read? it's the frequency? Luminosity? Energy? If we don't have anything more than the frequency to use, that is what is usually assumed to be the reference.
If you have a scan that directly states that it produces energy at the same level as a cosmic gamma ray burst or even more, that is what is needed. In fact, if you had shown only that, it would be enough, as that really is all that is left.
And of course, fiction is judged here at a level somewhat close to reality, but not so much. We are perfectly fine with giving something a hand-sized Sun a 4-C tier even though it makes no physical sense if that miniature sun has a feat on that scale (Like being used to blow up something with 4-C resistance). Again, if you have a statement directly saying, "It generates more energy than a gamma ray burst from outer space," that alone would scale to that level.
And of course, I can only comment on what is in the post itself, if there's more to it in the series, of course, my comment wouldn't touch on that subject because I don't know the series. If you have more information about the feat, I suggest next time to address all existing evidence in the OP instead of just giving more when people start to reply to the thread, you can't really complain about "It goes against the narrative of the series" if you don't give the narrative of the series beforehand.