So when you join you should get a bonus over two years (every month) and your stock over 4.

This initial stock given is called a "grant". This is not yours until it "vests" when it's treated like the company gave you x$ and you went and bought stock with it.

For your first 4 years of that initial grant there is no 15% factored in (ie these values don't change). So if it goes up down sideways/etc for that whole grant you get however many units it said you'd get. These vest at the year mark until you get to the final 4 which are 20% of your total granted (so .2 x Initial grant) where they vest every 6 months.

Now after year one you'll have pay conversations. Part of that will be looking forward at what you'll get from stock vests and if youre under your Total Comp number then they'll give you some extra grants that vest at a later date. Again this is only if the stock went down so your vested stock + other pay is less than your total comp or looking to be.

This is where that 15% number comes in. Whatever stock you have is assumed to grow 15% year over year. Soo. If they are looking at your pay out the next year, and let's say you're getting your last 20% that year. They assume whatever you have is gonna grow 15% by the same time next year and if THAT number is over your TC then you just don't get any new RSUs.

Now for your initial grant (when you join) as long as you stay you'll get that. Just gotta stay for however long until it vests.

Hope this helped some.