Yes, the last digit of the number 2 is 2. But no, Serge is not talking about just single-digit numbers 0 through 9. He is talking about a 6/40 lotto game (like NY Sweet Million, as his subject lines says) where we choose any 6 from 1 through 40. So the group 10,20,30,40 all end in 0; 1,11,21,31 all end in 1; 2,21,22,32 all end in 2, etc. Note that all 5 groups have 4 elements. That makes the combinatorial calculation relatively easy.
I think a 6/49 lotto is more common; but the relative percentages are similar. And I prefer to show the actual number of combinations as well as percentages, for those who prefer to avoid any rounding error. See the table below.
6/40 Lotto 6/49 Lotto
5+1 396 0.0028%
4+2 540 0.014% 3,960 0.0283%
4+1+1 5,760 0.150% 39,600 0.2832%
3+3 720 0.019% 3,960 0.0283%
3+2+1 69,120 1.801% 316,800 2.2655%
3+1+1+1 215,040 5.602% 924,000 6.6076%
2+2+2 25,920 0.675% 105,600 0.7552%
2+2+1+1 725,760 18.908% 2,772,000 19.8229%
2+1+1+1+1 1,935,360 50.421% 6,930,000 49.5573%
1+1+1+1+1+1 860,160 22.409% 2,887,500 20.6489%
TOTAL 3,838,380 99.999% 13,983,816 100.0000%
(Compare the totals with COMBIN(40,6) and COMBIN(49,6) in Excel.)
Note that a 6/49 lotto has an additional pattern, 5+1; that is, 5 numbers with the same last digit, and 1 number with a different last digit. Also, note that the group 10,20,30,40 has 4 elements, but the other groups have 5 elements (e.g. 1,11,21,31,41). That makes little difference for players; but it makes the combinatorial calculation more interesting.
My numbers are also "mathematically calculated", not counted by an exhaustive computer algorithm. But I don't know what difference that makes. Both are equally good methods, IMHO.
If anyone is interested in the combinatorial calculation, I would be happy to post some examples or the complete set. Or see the calculations described in https://www.lotterypost.com/thread/255827/2904841. They are for "poker" patterns; but it might give you some idea of the calculation. Also see the caveat about how to use such patterns ("It is tempting to think ...").
(Note: In that posting, I believe I use terms like "quad" differently from what is common among lotto aficionados. I mean: 4 numbers in the same "teen", e.g. 11,13,17,19.)