Sounds like you've done most things correct.
Set the end frequency to 200Hz.
Set your Graph Axis limits to a vertical scale of 45dB to 105dB and horizontal scale of 15Hz to 200Hz. This is the standard we usually use for most subwoofer graphs. You don't want to look at anything down to 2Hz because your meter and its calibration don't go that low.
Graph Axis Limits.jpg
Be sure to set the target up by selecting subwoofer and clicking the Set Target Level button (that doesn't look like a button) as the last thing you do before Measuring.
Target Settings.jpg
Post a graph and I can likely tell you what's wrong.
brucek