The numbering system used on beard trimmers does not correlate to the numbering system used on Barberís clippers a beard trimmer manufacture simply assigns a number gradient based on whatever spread his trimmer has (e.g. 1 - 5), etc.
The numbering system on a barbers clipper blades are actually standardized and relate to the average weekly hair growth so 0 to 1 is 1 week, 1 to 2 is two weeks, etc.
But there is Apsley no correlation necessarily between a one and a beard trimmer and a one blade on a barberís Osters. There may be by pure happenstance depending on manufacture but you canít count on it