Here is what I got to say, I think
Offset is.
when you have a Block, And it must spawn "Grass" or anythingelse (Collision..)
then when you can use lost of met.. Every Ms 100.(System-/Create object at image point)
something like this will pop up
-Choose object =Grass
-Layer =1
-X offset =0
-Y offset =50
-Postion to = Charater
-Image point =0
And you had a character of
W=50
H=50
When you start the layout, Every Ms there will spawn a Grass particle at the Hospot(red thing in image editor) of your character, then i will add 50 to the Y-as to your chracter. In rusalt the grass will spawn on the head(top) of your character every 100 ms
hope it helped