idxRange = 50

What does it mean? What do I do about it?

The default value of 50 does not adequately cover application usage of indexes.

Increase -indexrangesize.  Suggested settings are in $PROTOP/dbname.range.pf

The suggested settings give you a choice.  You can monitor just application tables and indexes or you can expand the range to include system tables and indexes.  There can be a surprising amount of activity in the system tables and it may be enlightening to monitor those as well.