On an older house, the meterbox has the main breaker-60A, 240V. Upstairs at the
subpanel are

15A
40A 240 V
20A

20A
20A 240V
15A
20A

The 40A 240 is for the kitchen stove
I don't know what the 20A 240V is-there isn't anything in the unit that
would need this. If there are electrical heaters, is it possible these are
fed from one leg each? The heaters are 110. Any suggestions for what it
could be? Two 20A circuits with one neutral?

How much more can the subpanel carry? can I add a 15A and a 20 A circuit
for a garbage disposal and Dishwasher?

charles