WordPress meta_query >= &

Looks like I found the solution.

I needed to use compare instead of operator in the meta_query

so

array(
  'key'  => 'vacancy_small_salary',
  'value' => $vacancy_small_salary,
  'operator'  => '>=',
  'type' => 'NUMERIC'
),

becomes

    array(
      'key'  => 'vacancy_small_salary',
      'value' => $vacancy_small_salary,
      'compare'  => '>=',
      'type' => 'NUMERIC'
    ),

and the same for the other query