New Employer Advice

Recently met with a CEO that wants me to play a role in their leadership team. However they want me to pick my salary and my commission. Stating year one will be less commission (new department) and year two will have more as the department grows. Total OTE in year two, would be around 500k. Total comp in year one with around 200k and the base being close to 115-130k (as quoted)

Anyone know what a good commission metric to give them would be? My issue is that I see this as a trick. I can overstate myself and ruin the job, or undersell and not get enough. This org has been pretty adamant in having me join and their HR Director stated, any number is a good number to give... help would be great and thanks!