Context: Study framed in the area of teacher training. Objective: To analyze the self-instruction booklets that elementary education future teachers designed and implemented to teach a subject related to the Numbers and Operations axis. Design: The research follows a qualitative, exploratory-descriptive methodology, using the content analysis method. Setting and participants: Sample composed of 85 preservice teachers who studied Numbers and Operations in Elementary School, attending the first semester of Pedagogy in Basic General Education with Mention in a Chilean university. Data collection and analysis: The activities and conclusions of the booklets are analyzed, considering the units of analysis: implemented learning objective, detected obstacles, type of activities and contexts, assessment of the pedagogical knowledge of the content and general experience. Results: The work emphasizes that future teachers mostly: design booklets associated with the first two years of elementary school; consider the objective associated to counting to 1,000; declare the epistemological obstacle; the activities are exercise-like; activities are posed without context; indicators associated to the subdomains of knowledge of content and of the students, and content and teaching of the pedagogical knowledge model of mathematics are not mentioned; value this resource to encourage mathematics learning. Conclusions: The work with booklets has allowed preservice teachers to approach teaching work for the first time, involving mastery and application of both didactic and knowledge of the subject matter for teaching numbers, which will improve during their training.