Does Teferi's Puzzle Box trigger before or after a player draws for their turn?

Teferi's Puzzle Box has a triggered ability that triggers at the beginning of each player's draw step. However, the normal draw-for-the-turn also occurs during the draw step. The key is understanding the order: the draw step begins, the turn-based action of drawing a card happens first (CR 504.1), and then triggered abilities that triggered at the beginning of the draw step are put on the stack (CR 405.1, 503.1).

Wait — actually, let's be precise. "At the beginning of the draw step" triggers trigger as the draw step begins, before the turn-based draw happens. Per CR 503.1, the draw step starts and "triggered abilities that trigger 'at the beginning of [a] draw step'" trigger. These go on the stack, resolve, and then the turn-based action (drawing a card) occurs. So the Puzzle Box ability actually resolves before the normal draw.

In practice: the draw step begins → Teferi's Puzzle Box triggers → the ability goes on the stack and resolves (the player puts their hand on the bottom of their library and draws that many cards) → then the player draws their one card for the turn as the turn-based action. This means the player ends up drawing hand-size plus one cards total.

For example: you have 4 cards in hand at the start of your draw step. Puzzle Box triggers, resolves, you put 4 cards on the bottom of your library and draw 4. Then you draw 1 more for the turn, ending the draw step with 5 cards (that you've never seen before, minus any you drew in Puzzle Box's draw).

This is confirmed by CR 503.1 (draw step structure) and CR 116.5 (turn-based actions happen after triggered abilities from the same trigger point have been placed on the stack and resolved).