What is a 409A valuation?
A 409A valuation is an independent appraisal of what a single share of your company's common stock is worth. It sets the strike price you grant stock options at. You need a current one before you can issue them.
It is not your fundraising valuation
The number you raised at is a preferred share price. A 409A values common stock, and common is worth less.
Preferred shares carry protections common does not, mostly liquidation preferences and anti-dilution rights. The appraiser discounts for that, so early-stage common usually comes in well below the preferred price.
Useful, rather than a problem. A lower defensible common value means a lower strike price, which means more upside for the team you are granting to.
How long it lasts
Twelve months, or until a material event, whichever comes first. Closing a priced round is the one most companies hit.