Drupal. How to replace the output of the result in views when applying aggregation to a field?

Question

Drupal

I added a field to define a new view field in hook_views_data_alter() . Specified a binding on the "uid" field from the DB table. Now I want to make a custom output for this field. If no aggregation is applied for the field, then I change the output in the custom handler via field_nahdler::render() . But as I understand it, if I hang, for example, count () on this field, then my handler no longer works out and the view draws the result somehow in its own way. If it outputs some result X, how can I catch it in the code and replace X with f(X)?