Environment Variables and JSON Parsing

I have a question about how numbers larger than a 32-bit integer are parsed and interpreted when writing to an environment variable.

We write a Unix Epoch timestamp to the _restart env var to reliably start a new session by perform a device reboot.

What is the range of integers that will reliably result in a device reboot and new session? If we write a number greater than 2147483647, the device does not reboot.