The regulatory approval of an academic qualification and authentication thereof are two different procedures that have different legal effects.
Authentication is the process by which the authorities of your country certify that the academic qualification is valid and has been issued by a competent authority to do so. In most countries this process is identified with the Apostille Convention.
Regulatory approval is the process by which the Ministry of Education of Spain equates your degree to its Spanish equivalent for the purposes of the performance of your professional career in Spain. This process can only be performed at the Ministry, except for master's and doctoral degrees, which may be managed through the Spanish universities themselves.
Those who indicate on the pre-registration form that their degrees have been approved, must prove so by attaching the resolution of the regulatory approval by the Ministry of Education of Spain. Should they fail to do so they may be excluded form the pre-registration process.