The 270 day rule starts on February 1st

From 1 February 2022, in order to travel to Spain with a vaccination certificate, the certificate must have been issued by the competent authorities of the country of origin at least 14 days after the date of administration of the last dose of the full course of vaccination, as long as the final dose of that course of vaccination was no more than 270 days ago. ( Approx 38 weeks)

From that time, the certificate must show the administration of a booster vaccination. Link to Official entry in the BoE .