ehhhhh.......i suggest picking up a book and learning to read basic piano/keyboard.....keyboard tabs were never meant to be made, TAB is for guitar, violin and other stringed instruments...piano has to many strings that piano tab just looks like a foreign language...
maybe ill answer your question though
c1 is low c and then c2, c3 ,c4 ,c5...etc... each octave has a number based on where it is from left to right on the piano