The value of the cards in the canasta counts as points in the meld; but the 300 bonus points for the canasta does not.
This means that in your example, you would be melding 120 points worth (50 for the Jacks, 40 for the 2s, and 30 for the 9s).
If instead your canasta were made of 4s instead of Jacks; then you would only be melding 95 points (25+40+30).
From the rules:
You can make the initial meld for your team by melding cards from your hand whose total value is at least the minimum count. The minimum count depends on your team's cumulative score at the start of that hand:
This initial meld from your hand must include either
a pure meld of at least three matching natural cards (with no wild cards), or
a wild card meld (at least three wild cards).
While these rules don't specifically cover the question of whether to count the 300 points for the canasta bonus; we can look in the rules for Classic Canasta:
The count of a meld is the total point value of the cards in it. To meet the minimum, a player may make two or more different melds. If a player takes the discard pile, the top card but no other may count toward the requirement. Bonuses for red threes and canastas do not count toward the minimum.
There is nothing in the American Canasta rules to imply that not counting the bonuses for canastas would be changed.