How to Execute PCL Command (ESC X m nn) on Epson Thermal Printer using C# to increase Font Size

const char ESC = '\x1b';

// Initialize printer
sb.Append(ESC + "@"); <-- Working too

sb.Append(ESC + "E" + (char)1); <-- Bold Weight it Works too
// Align center
sb.Append(ESC + "a" + (char)1); <-- it works too

Select font by pitch and point: ESC X m nn <-- so i tried it on my code by doing this:

sb.Append(ESC + "X"+ (char)15); it did not work but there is no error on code.
sb.Append(ESC + "X"+ (int)15); also tried this still the same.

sb.AppendLine(" " + "HELLO WORLD!" + "\n");

output:

it was Bold
but the text is still normal size not bigger

how do i proper execute the ESC X m nn PCL Command
same as i had on the bold weight ESC A (char)1

please help my reference document are this one.

<-- Page 104 of the PDF Doc.