It's now much clearer.
Single innings each, 250 overs left in the match. Even if a half-day is lost to rain, still 200 overs left.
Apart from Bradman, no team has ever won at Headingley by scoring 340 or more or by lasting more than 90 overs. Ever.
That means that quick, risky runs are not a solution for NZ. They need to ensure that they bat 120 overs. That means that ideally each of their top six batsmen aims to bat at least 20 overs.
If they do that their lead should be 350+, and they should have 120 overs to bowl England out, so that even a half-day lost to rain leaves them 75 overs on a wearing pitch with footmarks opening up for Craig.
So they need to set out their stall to bat 120 overs. And preserve their wickets in hand in case it rains sooner rather than later and they end up needing quick runs.