Thr php script is found here:

www.dmxzone.com/go?16444

What I don't understand is the MAX_SIZE*1024

Why 1024

And why does it keep saying 1mb limit if the limit is set to fx. 200bytes.

In MAX_SIZE you give the number of KB, the value is compared to Bytes, so multiplied by 1024.

If you set the MAX_SIZE to 200, it is 200KB or 204800 Bytes.