The Oneway platform requires that each row contain information for one or more observations with the same level of the X variable. If a row represents more than one observation, you must use a Weight or Freq variable to indicate how many observations the row represents.
When one-way data are in a format other than a JMP data table, sometimes they are arranged so that a row contains information for multiple observations. To analyze the data in JMP, you must import the data and restructure it so that each row of the JMP data table contains information for a single observation. See Example of Stacking Data for a Oneway Analysis.