Max pickup is the limit you can WS.

If you take a trip off the swap board, you're not limited by max pickup.

Now that you've taken a trip off the swap board, that credit is on your line and reduces your max pickup, as you've seen.

Therefore, yes, all you can WS now is a 1-day trip, as long as it's under 8 hours and change.

Edit - what OOfff said, both comments

You can, however, pick up another trip off the swap board to exceed the max pickup.