EWS reservation was introduced by the government for general category candidates. This is for all those candidates who are covered under any reservations and belong to economically backward sections.
The eligibility criteria of EWS certificate says that:

Family’s gross annual income should be below Rs. 8 lakhs from all sources such as agriculture, salary, business, etc. for the financial year prior to applying for the exam. Going by that, the salary should be of the year 2018-19 in your case.
Moreover, the certificate is valid for an year.