whn you display any number it shuld be one digit at a time sine ascii contains only 0 to 9 to display 123 you need to send 1 2 and the 3 seperatly and by adding 48 to that, it will get convert in ascii code
as we want to display 7 we send
lcd_data(7+48);
and 56 is ascii code for 7…
i hope you understood