Advanced compared to the first weapons.
Thermonuclear weapons were, after all, deployed just - what - six years(?) after the first bomb.
I think that it was either a fizzle, or that it was a fake. 550 Tons is not a realistic figure for a nuclear explosion.
Of course it is, we had numerous 10, 20, and 50 ton yield nukes.
Now the question of it being realistic for a first device is another matter. Historically those run in the 10-40 KT range. The NKs likely got some of their designs from Pakistan, whose first was in that range. However the basic designs for the little guys are pretty available, and given that they got some help from the Kahn network, they might have tried to go that way. They do seem to have gone the plutonium route, which allows for the smaller yield weapons.
But on balance, a fizzle seems most likely.