Ok, now I know what my problem is. My 248KB file is less than 250KB but greater than 250,000B
A little clarification for those who are confused. In computers, 1 kilo does not equal 1000 (10^3), it's actually 1024 (2^10). mega (2^20), giga (2^30), tera (2^40) and whatever's after that also differ from the metric prefixes. So after a quick calculation, my 248KB file is actually (248KB * (1024B / 1KB)) = 253,925B.
Mike