The article presents the results of a study that examines the task of transcoding spanish verbal numerals to Arabic numerals. The evidence stems from a number dictation test applied to 118 students from grades 1 to 4. Results indicate that the behavioral effectiveness of children during the task follows a discontinuous process characterized by abrupt ascents and descents when increasing numerals are being incorporated. This paper discusses some characteristics of the numbers that are associated with the difficult task of being transcoded.