Structure Spawning and Offset

Structures generate facing the positive x and z axis; essentially, the default option is the same thing as the game placing down a structure block on top of the ground, and triggering it. If rotation is randomized, it uses the same rotation system as the structure block.

I learned this the hard way. 

Mcreator's instructions are kind of vague, but through a bit of trial and error, I've learned the following that might be useful to you:

• If you want the structure to be centered on the chosen location, you'll need to subtract half the width/length of the structure from the z and x values respectively. (And you'll need to have an odd length/width if you want it to be exact.
• If you don't want your structure cutting through terrain or generating floating, there are a couple options: making a condition that checks if the terrain is viable, making procedures that adapt the structure to the terrain, or just making a structure in such a way that the terrain doesn't really matter. (If it's big enough, the surrounding terrain won't make much of a difference.) 
• That last one is important: By default, structure only check the single block they generate on. Unless you add additional procedures, you can get stuff generating on cliffs, partly buried, partly underwater, inside other features, etc. It's not always clear whether biome features generate before custom structures, but you're better safe than sorry.

I have the same issue. But thanks to him he helped even though this is a loing time ago