This is the zone that the stats relate to
Pixel Diff 
This is the average difference between the pixel values in the image and the reference image. This relates to Min/Max Pixel Threshold and can be useful to help tune those values.
Alarm Px [5954 (34%)]
The number of pixels in the zone whose difference were between your defined min/max pixel thresholds. If this is between your defined min/max alarmed pixels then go to next step.
Filter Px [4906 (28%)]
The same value after filtering with your defined filter. If this is between your defined min/max filtered pixels then go to next step. In this case you have had 1048 pixels filtered out because they were in groups less than 3x3 in size.
Blob Px [4858 (27%)]
The number of pixels that have been aggragated into blobs that are at least your min blob size and less than your max. In your case 48 pixels have been eliminated. You probably had one 48 pixel blob, but it may have been 1 x 18 + 2 x 15 etc.
The actual number of blobs that fit the blob size criterion.
Blob Sizes [3797 (21%)]
This gives the minimum and maximum blobs sizes. As you only have one it is both.
Alarm Limits [178,141-319,186 ]
This is the extent of the alarmed area (the blob above in your case) in image co-ordinate terms, x1,y1 - x2,y2
This is an arbitrary score that is intended only to have a way to quantitatively compare events to see which is more significant.
Hopefully that will help you understand the stats a bit more. If you have several zones then you may gets stats generated for each zone. It may be helpful to also switch on diagnostic images for a short period which will dump images at each stage of the process as it's often easier to understand visually. One day I'll find the time to write an article about all this with illustrations