为什么chr（）函数适用于有效范围（0 ... 255）之外的少数字节值而不适用于其他字节值？

I'm using PHP 7.3.4 on my home machine that runs on Windows 10 Home Single Language 64-bit operating system.

I come across below statement from PHP Manual:

Values outside the valid range (0..255) will be bitwise and'ed with 255, which is equivalent to the following algorithm:

while ($bytevalue < 0) {
    $bytevalue += 256; } 
$bytevalue %= 256;

I'm able to print the single character string for bytevalue which is outside the valid range i.e. outside(0...255) using the built-in chr() function.

But for few values like chr(-598), chr(-813), chr(-1059), etc. it's displaying the � character. Why it's not displaying the relevant character specific to the newly calculated bytevalue according to the above algorithm?

I also want to know from where this � came as it's not been present in any of the ASCCI compatible character encodings?

Please help me out in this regard.

Thank You.