In this passage, the 1920 LDS edition twice replaced the plural were with the singular was for the subject noun phrase “the number of their dead”. In both cases, the text refers to the possibility of a specific count; thus the singular was is correct according to standard grammar. In the first case, one could consider the clause “the number of their dead were not numbered” as redundant because of the repetition of the word number. On the other hand, if one interpreted the meaning as ‘the dead were not numbered’, then the use of the plural were would be perfectly acceptable. But it is also possible to interpret the verb number as meaning ‘calculate’, with the result that the meaning here is ‘the number of the dead was not calculated’. Under this interpretation, one could argue for grammatically emending the were to was. A virtually identical example of the use of the noun number with the verb number is found in Alma 3:1: “now the number of the slain were not numbered because of the greatness of their number” (as noted below, the 1920 edition did not emend this instance of the plural were to was).
For the second case of editing were to was here in Alma 44:21, we have a statement regarding the number of the dead—that it was “exceeding great”. In this case, the original use of were seems to be based on proximity rather than meaning. Number agreement based on proximity can be found in the original text; see, for instance, the nearby discussion under Alma 40:19.
Under Mosiah 2:1–2, it was noted that the be verb could be either singular or plural in the specific phrase “there was/were a number (of X)”. Similarly, the original text allows either singular was or plural were for the subject noun phrase “the number of X”. In the following list of examples, the word number refers to a specific count, and in only one case (marked with an asterisk) does the original text have the singular was:
In only one of these other instances has the were been edited to was (namely, in 3 Nephi 12:1, and once more by the editors for the 1920 LDS edition). In other words, there are still examples in the text where proximity determines the grammatical number for the verb associated with the subject noun phrase “the number of X”. The critical text will restore the three original instances of were, twice here in Alma 44:21 and once in 3 Nephi 12:1. In all three cases, the original plural were is the reading of the earliest textual sources.
Summary: Restore in Alma 44:21 the two original cases of were that have been edited to was for the subject phrase “the number of X” (here the noun number refers to an actual count); similarly, were will be restored in 3 Nephi 12:1.