> But how do I proceed from there with actual planning or budget?

You make up the number you wanted to hear in the first place that ostensibly works with the rest of the schedule. That’s why engineering estimates are so useless - it’s not that they’re inaccurate or unrealistic - it’s that if we insisted on giving them realistic estimates we’d get fired and replaced by someone else who is willing to appease management and just kick the can down the road a few more weeks.