Scruffy Bar Chart Question

Hi-

I have been using Scruffy for a couple days and it's worked out really
well. I am stuck though getting a bar chart to work with a single
line.

Here's what I am doing:

general chart stuff..graph.new...etc
...
my_graph.add(:bar, 'GOAL', [250,350])
my_graph.add(:bar, 'ACTUAL', [150,200])

This works, but what I was is a SINGLE Bar with one value layered over
the other:
my_graph.add(:bar, 'GOAL', [250])
my_graph.add(:bar, 'ACTUAL', [150])

This does not render anything, how come??