It is an interesting thought. If you consider the implications, one, safely, can rule that out.
The Victorians were not very concerned with the illiterate in England. They, certainly, would not have considered illiterate peasants in India. The local administrators would not have been concerned with the lower castes.
If the stamp was overprinted - it, clearly, is not an overprint but a very crude handstamp - at all, it, under no circumstances, would be overprinted for the benefit of illiterates.
• Illiterate people would not be able to read "4A" either.
• An illiterate person would have been the very last person to stick a stamp on a letter. That person would not have been able to write a letter to stick it on. Nor would that person be able to address a letter to stick it on.
• Such illiterate people, unlikely, could even afford 4 annas to waste on a letter.
It, also, will not have been overprinted for the benefit of an illiterate postman or post-office clerk. If they would be illiterate, mail would not be delivered to the addressee.
There are two British stamps (1 January 1883, SG 159 and 162) that had a large value printed together with the value spelled out as on earlier issues. This was done to make the value more visible for the clerks that, usually, worked in dark, candlelight rooms. This, certainly, is not such an example. Such an official issue would have been listed.
The first question that requires an answer is, was the "4A" applied before, or after the cancellation? It is impossible to tell from a scan. The odds are the latter is the case and someone with a stamp kit – although the crude nature of the stamp does not rule out a knife and a potato – has had some fun with a cancelled stamp.