This is where the representation part comes in and hopefully your students would come to that conclusion too - and then try to figure out a better way. Suggestion: print out one sheet for each student and they can cut it up - then try to find ways in which they can have a simple representation for the letters by giving them words with too many letters so they have to represent it in a different way.
I’ve used the example of the hash mark system. if someone wanted to, they could represent 23 of something with 23 lines on a paper, but that isn’t very clear. So we make lines through groups of 4 (to make 5) and it’s easier to read - and although the group doesn’t have 5 lines, you can see that the 4 lines with the line through it is a representation. I then gave them bigger numbers (100+) and they saw how confusing all of the groups of 5 were and they created their own grouping system to make it easier (all levels of abstraction and representation).
This animal activity is similar in the way that one elephant could equal “A” and two elephants equal “B”, but really the students need to come with with a representation with the limits of the sheet of cards and then have multiple test (and iterations) of the solution.
Hope that helped…