By default, JIRA will limit the search results to 1000 items. 

When the Agile Tools & Filters for Jira Software search returns more results, the following message will be displayed:

There are two possible ways to proceed: 

• Narrow your search criteria to limit search results.
• The maximum search limit is defined by the jira.search.views.default.max property.
  Contact your JIRA administrator to increase it.