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Substr configuration key "start" description not correct.
Enter a descriptive title (above) relating to class Substr, then describe the problem you have found:
The documentation of the migrate process plugin substr is a bit confusing.
The configuration key "start" is actually the offset, not the start position. The example 'Marie Skłodowska Curie' shows the correct use? The resulting string starts at position 7, meaning an offset of 6. Maybe the name of the key or usage can change in the future?