Monero base58 is not like Bitcoin base58, bytes are converted in 8-byte blocks. The last block can have less than 8 bytes, but at least 1 byte. Eight bytes converts to 11 or less Base58 characters; if a particular block converts to <11 characters, the conversion pads it with "1"s (1 is 0 in Base58). Likewise, the final block can convert to 11 or less Base58 digits.
Due to the conditional padding, the 69-byte string will always convert to 95 Base58 characters (8 * 11 + 7); where 7 is length of the last block of 5 bytes.
Base58 encoder and decoder