Normally with a standard draw lottery, you have the option of having the machine pick all the numbers or manually picking the numbers however with Canada's Lotto-Max you have the option of picking one set of seven numbers and the machine will pick two more sets of seven numbers automatically or having the machine pick all three sets of seven numbers.
With a standard draw lottery, the advantage of picking your own numbers is to avoid overlap of number combinations, ie.: if one set of numbers already contain the numbers 6-13-30 then there's no point in having all three of those numbers in another set that you buy. With machine picked numbers, there's a chance that the various sets would share some numbers but you can avoid this if you picked your own.
Unfortunately, with Lotto-Max, since only one third of the sets are picked by you and the other two thirds are machine picked, there's no way to maximize your chances by avoiding overlap.
Note that the advantage of manual picking can be calculated but is so incredibly slim that it's not really worth bothering about, still every little bit helps.
An interesting feature of Lotto-Max is that once the jackpot hits $50 million, it stops growing with each additional million that would've been added to the jackpot being a separate 7 number draw called a Maxmillion draw. For example, this Friday's Lotto-Max draw is one draw for $50 million and 29 draws for $1 million each, only the main draw has subsidiary prizes.
For some reason, the Canadian draws tend to have a lot of machine picked numbers in addition to the numbers that you pick. They also have a strange way of dealing with bonus balls where you match one of your selections that didn't match to the bonus ball. That is, the bonus ball is drawn in the same draw as the white balls instead of out of a separate draw as it is stateside.