what should the footers look like. if you are expecting sum(1.1) = 1.1.1 + 1.1.2 to be 2.2.3, then you need to do the math yourself as you can't 'add' strings. you could do something like:
tottext(sum({table.level1},{group}),0,"") +"." + tottext(sum({table.level2},{group}),0,"") + "." + tottext(sum({table.level3},{group}),0,"")
HTH