How many students of R' Akiva died during sefira?

We are all familiar with the number 24,000 (12,000 pairs). In truth, this number seems very high, he had 24,000 students in his youth and only 5 when he was older? I just saw that there are actually multiple opinions as to how many students died.

1. 300
2. 12,000
3. 24,000
4. 48,000
5. 80,000

2-4 are clearly variations on the 24,000 as the 24,000 was expressed as 12,000 pairs. 

It's fascinating how the number that makes sense, 300, is not the number that we know but rather we know the exaggerated number.