Minimum Legal Re-raise before All in

I posted a picture below for clarity.

• Blinds 100 / 200
• SB = posted 100 blinds
• BB = posted 200 blind
• UTG = Bet 400
• Low Jack = Raise 600
• High Jack = Goes for all in 900
• Cut off = 1,200

Is this correct a computation? 1,200 is the minimum legal amount of re-raise after all in? Can someone explain it to me if I am wrong, and provide some resources like TD rules etc.

The rules differ between Limit and No Limit Hold'em.

In most No-Limit Hold'em games, the rules are as follows (BB = 'big blind'):

• The first pre-flop raise must be by 1 BB (i.e. to 2 BB or more).
• The first bet on any other street must be at least 1 BB.
• For other raises, the minimum raise is the size of the last raise.

For example, if the current bet is 300 and someone raises to 1300, that's a raise of 1000, so the next player (if raising) must raise to at least 2300.

(There are more complicated rules when a player goes all in with fewer chips than are required to meet the minimum raise, but those aren't relevant to the specific question asked.)