I don't trust English advetisers' mathematics.

Well, not since I saw 500gms of a Butter substitute on sale for the price of 250gm: alongside a label PROUDLY proclaiming "50% extra FREE".

I must confess I have NO idea whether they mean it's really 120% brighter or just a modest 20%.
This one set me back a penny short of 10 Quid.
Two "Long-life" would have been, logically, a tad short of 20 Smackers, with a caveat to change both together.

Ever the nosey old sod  curious Gentleman, I enquired about said
"Brilliance" range:- A mere £20 EACH. Nein danke.
NOW I DO want to know whether it would be worth it for a whacking great 120% more light.
Or pointless for a modest 20%.

BTW Mr Spill chucker :-
"Either spelling can be used, but many people prefer enquire and enquiry for the general sense of “ask”, and inquire and inquiry for a formal investigation:"