Ok, I get what you are saying.
I should tell you, it is not normal to separate seconds from hundredths of seconds with a colon. Normally a decimal point is used for this. A colon is normally used to separate hours from minutes or minutes from seconds, in other words where the is a difference of 60x between a "1" on the left side of the colon and a "1" on the right colon. Where there is a difference off 100x, it's more normal to use a decimal point. But this is your project...
I would simplify your code by using the sprintf() function:
char buff[10];
...
sprintf(buff, "%02d:%02d.%02d", mins, secs, hundredths);
...
P.print(buff);