why does some of the fields in the SH starts with # , and others not .
The # sign represents numeric fields which can be used in stats to calculate an aggregate value whereas the a symbol represents alphanumeric and cannot have its values calculated by a stats command
If you have a numeric field called duration, you can do this
| stats avg(duration)
If its alphanumeric, you will not get a value returned from stats
The ones with # are numerical fields.