One is the Programa de Resultados Electorales Preliminares (Preliminary Electoral Results Program, known by its initials PREP); the second was the Conteo Rápido (Quick Count). Although the two were often confused, they were in fact two separate systems. The PREP is a mechanism to make public the results of the election. As soon as the polls closed and the votes were tallied in each polling place, a copy of the acta de escrutinio (the official tallies from the polling place) was sealed in a special envelope with a transparent window. It was then sent to a Center for Information Collation and Transmission (Centro de Acopio y Transmisión de Datos or CEDAT) that was located in the corresponding electoral district. There, the information was captured and transmitted to the central offices of the IFE for public dissemination. The information was then backed up and made public on the IFE website and a number of mirrors. The PREP is not an estimate or a statistical exercise, but rather the full unofficial returns from each polling place, as they were computed at the polls on the day of the election. They are not official returns, since the tallies must be certified by the District's Electoral Council before they become official. The PREP would continue to collate data until all polling places reported or until the early morning hours of Monday July 3. If the tally sheets contained certain inconsistencies (e.g., blank entries rather than zeros, illegible totals, etc.), then they were reported separately, under the heading of Irregular, as per prior agreement between the parties, and were not added to the totals as they were received. Where possible, their results were added when the final report was made on Monday morning. In the PREP, election results were posted as they were being received by the IFE. Calderón quickly overtook a very early lead by López Obrador and kept a diminishing lead until the end. Quick count The Conteo Rápido (Quick Count), on the other hand, was a statistical attempt at predicting the trend of the election. On the night of the election, a random selection out of a representative sampling of 7,636 polling places was to be selected, and statistical analysis would then be performed in an attempt to predict the winner. The agreement regarding the Conteo Rápido was as follows: Using the results that had been obtained by 10:00 pm on July