Stripe Create Usage Record Error - Timestamp Must Be Before The Subscription's Current Period End Time - Date.now()?

I'm trying to create a stripe usage record for a customer on a metered plan.

When I'm using timestamp Date.now() in my request. The error I'm receiving is

"Cannot create the usage record with this timestamp because timestamps must be before the subscription's current period end time"

This seems self-explanatory. But given the subscription's current period end time isn't for another 14 days, how can Date.now() not be before this.

        await stripe.usageRecords.create(
            'si_EwzQ....',
            {
                quantity: 2,
                timestamp: Date.now(),
                action: 'set'
            }
        )

Is this because the current subscription period is a trial? Or have I misunderstood something here?

They're using a slightly different timestamp here. You must divide it by 1000.

So Date.now() / 1000