Update README.md

Signed-off-by: Can Zhao <[email protected]>

generation/maisi/README.md

@@ -141,6 +141,7 @@ The information for the inference input, such as the body region and anatomy to
 
 #### Recommended spacing for different output sizes:
 According to the statistics of the training data, we have recommended input parameters for the body region that are included in the training data.
+The Recommended `"output_size"` is the median value of the training data, the Recommended `"spacing"` is the median FOV (the product of `"output_size"` and `"spacing"`) divided by the Recommended `"output_size"`.
 |`"body_region"`   |percentage of training data |Recommended `"output_size"`| Recommended `"spacing"` [mm]|
 |:--------------------------------------|:--------------------------|:----------------------|---------------------------:|
 | ['chest', 'abdomen']                  |                      58.55% | [512, 512, 128]           | [0.781, 0.781, 2.981] |