I'm not an expert on graphs but I too know how to read graphs. The problem is whether I'm capable of putting my thoughts into words 
I made an assumption in my original post because I didn't knwo what DSI was. Actually if I had the capability to edit the graph, which I didn't because it's not my graph- something I simply picked fromthe Internet, I would have removed DSI and wrote 'number of computers sold' which is my assumption.
I hope that clarifies it.
Tanit DSI (Day Sales of Inventory) measures the performance of a company. The lower the DSI, the better the performance (... unless here DSI means something else, of course!)
Edit: Oh no. You got me. I misinterpreted the graph! I swapped the two companies! I'm sorry :(
Please refer to the corrected version below:
From 1996 to 2005, HPQ sold more computers than Dell did every year with HPQ's highest sales in 2001 at around 42 DSI and Dell's highest in 1996 at around 11. The narrowest different was in 1996. The graph shows HPQ sold twice or more computers than Dell every year except maybe 1996, close to twice.