Bava Batra

On that day [the price of a pair of] birds fell  to a quarter [of a denar']. IF ABOVE IS WRITTEN etc. Our Rabbis taught: The lower [section] may be corrected  from the upper [one] where one letter [is missing], but not in [the case of] two letters; for example, HaNaN from HaNaNI  or 'ANaN from 'ANaNI.  What is the reason  why two letters [must] not [be replaced]? [Because] a name of four letters might occur and these  would represent half of the name! If so, [in the case of] one letter also, might [not] a name of two letters occur and this  would represent half of the name? — But this is the reason [for] two letters: A name of three letters might occur, and these would represent the greater part of the name. R. Papa said: It is obvious to me [that if] SeFeL  [appears] in the upper [section].  and KeFeL  in the lower [section], the latter is always to be taken as a guide.  R. Papa, [however], inquired what [is the ruling if] KeFeL [appears] above and SeFeL below? May this be attributed  to a fly,  or not? — This remains undecided. In a certain [deed] there was written, 'six hundred and a zuz'. R. Sherabya sent this [enquiry] to  Abaye: [Is the entry to be interpreted as], 'six hundred istira  and a zuz', or perhaps, [as] 'six hundred perutoth  and a zuz?' — He replied to him: 'Dismiss [the question of] perutoth which [could] not [have been] written in the deed, since they are counted up