Summary indexing in Splunk produces a lot of psrsvd_* fields. And below is the explanation of what they actually stand for.
psrsvd stands for "prestats reserved"
These fields are an artifact of using the si* version of reporting commands. The fields are specially named so that on retrieval from the summary index, the reporting command (chart/timechart/stats) can properly decode the information.
The general pattern is psrsvd_[type]_[fieldname], although some types are not scoped to a field
1. ct = count
2. gc = group count (the count for a stats "grouping", not scoped to a field)
3. nc = numerical count (number of numerical values)
4. sm = sum
5. ss = sum of squares
6. v = version (not scoped to a field)
7. vt = value type (contains the precision of this field)
So for example, the count for a field named 'foobar' is stored as psrsvd_ct_foobar.