The image at the bottom of the diagram should give you a good indication of the angle that you should be chopping at. This is for cross grain chopping, you want to avoid coming in at 90°, I believe 45° is the general rule but I could be wrong. So it would be a more acute angle if thats what you mean. Going with the grain generally used for splitting you should notice that it bits in readily at 90°. Cross grain at 90° mine will not generally go past the bit unless it is something like a 1" limb, at the proper angle though it should bit in fairly deeply unless you are working with a well seasoned hardwood in which case much more effort is required regardless of the tool. With the Mini I find you can get a lot done if you are open to different tricks to help along the way. For example making a wooden wedge to help splitting larger wood, and using the notch and stomp method rather than trying to chop clear through a 5" dried limb.
/\ This photo sort of sums up the angle that I use to start a v using an 8oz hatchet. It's a light tool so angle and accuracy are more important than with a heavier tool in my experience. The only other advice I can give is to use your wrist like you would with a fishing pole or properly using a hammer. Not like that guy using a tack hammer for framing work, white knuckles stiff wrists and trying to power it using his shoulder and upper arm. I get the feeling you'll understand that reference. I spent a summer framing houses. I'm still more accurate with my Craftsman (probably Vaughan) framing hammer than the typical tack hammer most home owners use ;-)