uber RSU choice

For my offer base 157K, RSU 390K/4 years. Instead of using total 420K divided by 409a price, can I ask recruiter to update the offer as number of shares like 12000 ? Which way is better ? 1) total RSU value divided by 409a price. 2) exact number of shares . The concern for "total RSU value divided by 409a" is if you onboard after 2 months, and 409a price become larger, your total number of shares will be less.