“(2) [subject to sections 93(8) and 93A(7) of this Act] on an appeal against the determination of a penalty under section 100 above section 50(6) to (8) of this Act shall not apply but – (a) in the case of a penalty which is required to be of a particular amount, the [First-tier Tribunal] may – (i) if it appears … that no penalty has been incurred, set the determination aside, (ii) if the amount determined appears … to be correct, confirm the determination, or (iii) if the amount determined appears … to be incorrect, increase or reduce it to the correct amount,”