Loading multi-array problem

Can anyone tell me why the variable y is not loading into the array as y:+28?

Graphics 1024, 768
Global tarr[50,3], x=0, y=30 

For n=0 To 49
	tarr[n,0]=n
	tarr[n,1]=x
	tarr[n,2]=y
	If y>700 y=30 x=132
	y:+28
Next
y=30 x=0
For n=0 To 49
	DrawText "Frame# "+tarr[n,0]+"  x = "+tarr[n,1]+"  y = "+tarr[0,2],x,y
	y:+15
	If y=>400 x=250 y=30
Next

Flip
WaitKey

It just don't make sense.

Because you've got...
tarr[0,2]
rather than...
tarr[n,2]