The team for this IG has 59 members, and I think it's been similar for each time it's been held (except the first, in London, where there were over 100). Of course Invictus also supports training (in RL and on online platforms such as Zwift) and the IG Foundation says in 2022 it helped 235 people - but the website is contradictory in places. There may well be substantially more.
But for context:
I'm not sure how many served in total in Afghanistan - BBC reported a total over 70,000 (with over 450 fatalities). Iraq about 53,000 (sources vary, which is why it's hard to be sure.
The military charity SSAFA says it helps around 66,000 people per year (all veterans, not just those who served in Afghanistan and Iraq)
Invictus Games is however an excellent initiative, and it definitely helps to keep the ongoing needs of veterans in the public eye, even though its actual reach is quite small compared to other military charities.