California ADU law: impact fees for units larger than 750 SF

[Gary Miguel]

SB 13 bans impact fees for units smaller than 750 SF, but for units larger than that it has this text:

"Any impact fees charged for an accessory dwelling unit of 750 square feet or more shall be charged proportionately in relation to the square footage of the primary dwelling unit."

What does that mean in practice? Say the primary unit is 2000 SF and the ADU is 1000 SF, and there's a fee of $1 per SF of new construction, what is the calculation to determine the fee for my project?

Thanks!