The error indicates that your indexing was rejected due to the record with the objectID 1234 being too large for indexing. As you can see from the error message, the record surpasses the maximum allowable size of 100KB, specifically totaling N bytes.
To resolve this issue, you can remove any unnecessary attributes from the record so that it can be indexed (as detailed in our guide to reducing record size).
Please also note that when you receive this error, the entire payload of the update/batch operation will be rejected (and not just the record mentioned in the error message). After reducing the size of any oversize records, you'll need to retry indexing all records contained in the original batch.