Wolfram Language (Mathematica), 45 bytes

FromDigits[Plus@@PadLeft@IntegerDigits@#,19]&

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Wolfram Language (Mathematica), 30 bytes

Total@PadLeft@#~FromDigits~19&

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Takes input as list of digits as @my pronoun is monicareinstate suggested and saved 13 bytes (IntegerDigits)

-1 byte @LegionMammal978