TLDR:

Lua >5.3 supports 64-bit integers, but encode_number rounds to 14 significant digits. This causes values to be unnecessarily rounded even though Lua and WASM support them.

Related to the PR in the original json.lua implementation here - rxi/json.lua#42

Example:

Spin up a process using aos and add the following Handler.

Handlers.add("test", "Get-Number", function (msg) 
  local exampleValue = 951824235837328
  ao.send({ Target = msg.From, Value = exampleValue, Data = exampleValue })
end)

Value and Data are rounded and returned as 951824235837330. If tostring() is used, the correct number (as a string) is returned.