I fail to understand how the YC deal operates as a SAFE with 7% equity? If the SAFE is a non-priced round, then the amount of equity the investor gets is decid

I fail to understand how the YC deal operates as a SAFE with 7% equity? If the SAFE is a non-priced round, then the amount of equity the investor gets is decided when the conversion happens, so it is an unknown, which is why a cap exists. Is YC taking 7% + the conversion?