"The first digital images are expected to be put online in the second half of this year. All of the manuscripts, including the most delicate ones, will eventually be scanned, and viewers will be able to examine them from a variety of angles.
Digitalizing the library will be a mammoth task, involving 43 quadrillion bytes. (A byte is a unit that is used to represent an alphanumeric character.) In the end, about 40 million pages will be available for all to see. The Vatican won’t say how long the whole project will take. "
Your arithmetic. 40 quadrillion divided by 40 million is a billion, not a trillion.
Since ancient documents are unlikely to be in English, a byte will not suffice for one character. Unicode requires up to four bytes per character.
Since they are almost certainly going to show the original document, rather than a transcription of it, the byte count for characters is irrelevant, anyway. They’ll be putting up image files, probably in several different resolutions for each page, which may well require a gigabyte per page.