I'm getting incorrect data usage

Total=$ts(mt, m, r6d, a0d)$ 118.9mb

Sum=$ts(mt, m, r6d, r5d)+
ts(mt, m, r5d, r4d)+
ts(mt, m, r4d, r3d)+
ts(mt, m, r3d, r2d)+
ts(mt, m, r2d, r1d)+
ts(mt, m, r1d, r0d)+
ts(mt, m, r0d, a1d)$=sum{d6=$ts(mt, m, r6d, r5d)$,d5=$ts(mt, m, r5d, r4d)$,d4=$ts(mt, m, r4d, r3d)$,d3=$ts(mt, m, r3d, r2d)$,d2=$ts(mt, m, r2d, r1d)$,d1=$ts(mt, m, r1d, r0d)$,d0=$ts(mt, m, r0d, a0d)$} 237.9mb

Phone shows 258mb!

When I checked each day like this:

$ts(mt, m, r6d, a0d)-ts(mt, m, r5d, a0d)$ == $ts(mt, m, r6d, r5d)$

$ts(mt, m, r5d, a0d)-ts(mt, m, r4d, a0d)$ == $ts(mt, m, r5d, r4d)$

...

$ts(mt, m, r0d, a0d)-ts(mt, m, a0d, a0d)$ == $ts(mt, m, r0d, a0d)$

None of these matched!

Am I doing something incorrectly?