"I bought one kilogram of sugar."
Why is one kilogram after suger in this one? I'm pretty sure it accepted kilogram before sugar in a different one.
Apparently you're referring to Shopping 2. It would be helpful if you could try to find the other example, but I believe I can answer you.
The lesson that you're referring to tends to focus on placing the item before the amount. This is more common, but it can be reversed.
Option 1: A + を + quantity + verb.「さとうを一キロかいました。」
Option 2: Quantity + の + A + を + verb.「一キロのさとうをかいました。」
The meanings are the same, just a difference in what you are emphasizing. In option 1, you are emphasizing the quantity. In option 2, the emphasis is on what you are buying. Effectively, the same thing is being said.
You can use this in numerous cases:
Eat more vegetables 「もっとやさいを食べて」or 「やさいをもっと食べて」
Take my hand firmly「しっかり手をつかまって」 or 「手をしっかりつかまって」
Unless one of the lessons is not accepting a Japanese translation in one of these orders (used correctly of course), this shouldn't be an issue.