Which letter carries the numeral 400 in Church Slavonic, uk or izhitsa?

Why it is open. The manuscript tradition gives 400 to uk. The printed Church Slavonic tables give it to izhitsa. Both usages are attested and they cannot both be right for any one book, so a number in the four hundreds cannot be read without knowing which tradition the source follows. The atlas records the value on both letters for that reason, which is a compromise rather than an answer.

What would resolve it. A survey of dated Slavonic manuscripts and early printed books recording which letter carries 400 in each, by region and by period, which would establish whether the printed usage is an innovation of the printers, an inheritance from one recension, or a correction toward the Greek series.

Field. Slavic palaeography and the history of Slavonic printing