How can I change the default size of the returned aggregations (10) in kibana “create new rule”?

To create new rule in kibana ,when I selected "Threshold Aggregate query results to detect when number of matches exceeds threshold." , by default size is 10:

"aggregations": {
"eventActionGroup": {
"terms": {
"order": {
"_count": "desc"
"size": 10,

How to change size ?

Can you elaborate what sort of rule you are looking to create here please?