When an initiative proposal and an alternative proposal are put to the vote on the same day, what choices does the voter have?

Political Constitution of Costa Rica (ConstituciónPolítica de la República de Costa Rica)

http://aceproject.org/ero-en/regions/americas/CR/costa-rica-constitucion-politica-de-la-republica

Law 8492 Referendum regulations (Decreto 8492 para laRegulaci?n del refer?ndum)

http://aceproject.org/ero-en/regions/americas/CR/costa-rica-decreto-8492-para-la-regulacion-del

Law 8491 Citizens’ Initiative (Ley 8491 de IniciativaPopular)