Tiers is French for a third (1/3)
Upper means what is above.
Lower means what is under.
Lotto is a kind of actual keno game without second set, only that there is no payout for the 0 score. Mostly the amount of numbers drawn is the same than the combination size. When more balls are drawn, they are considered being a second chance because there are not enough winners with the original set. In some cases the lottery had too much cash and didn't want to raise the payout.
Numbers are hole numbers, integers. 0 is an integer, negative numbers are not used.
If you do not understand the terms, they were invented so you don't understand or connect to common knowledge, say scam or fraud.
When you have 46 numbers, you don't have tiers. When you have 45 numbers, you have tiers.
When you have 33 numbers, you don't have low and high numbers, only sets. You have 3 tiers of size 11.
When the set size is a prime number, you have no equal parts. So you have no high/low, no odd/even, no tiers etc.
At roulette you have 37 numbers. There is for example RED, BLACK with ZERO, but not only red or black. We don't look at American roulette. The bank advantage is higher there.