The tokenization process for SELFIES involved several steps. First, each SELFIE string was split at bracket delimiters ('[]'), which naturally separate the molecular fragments in the SELFIES notation. These fragments were collected across the entire dataset to create a comprehensive dictionary, with each unique fragment assigned a numerical token. This process yielded our final vocabulary of 69 tokens. The maximum length of 45 tokens was determined by analyzing the token length distribution across the dataset, ensuring coverage of all molecular structures while maintaining computational efficiency.