Please help big bros, i am a very new hand & also a 窮 new hand

. Bought a new cheap price tank $90(sales said from Taiwan wor) around 3 weeks ago, the size is 23.5"(L) * 9"(W) * 11.5"(H). Now I want buy a new light and see many old post. But never see the size(long side) is 23.5", seems the standard is 24"...
My question are:
1) Is my tank size is weird and non-standard?
2) Any bros know have this kind of light for 23.5" size use?
3) If no this kind of size, what can i do ar?
4) Not a lighting question, but 順便問

la how to calculate how many liter of water my tank can contain ar because may be later update my filter to 圓桶 filter, now using 懸掛式, mo mud $$ ma.