Since you know the amount of copper stuff that you are using, you can calculate how much CO2 and O2 would theoretically be produced by working out the moles of the copper stuff (mass = moles x mr)
Equation 1 is 4CuCo3 = 2Cu2O + 4CO2 + O2
Hence the moles of O2 = the moles of copper stuff / 4
The moles of CO2 = the moles of copper stuff
1 mole of any gas will occupy 24000cm cubed so times the number of moles of O2 by 24000 and the moles of CO2 by 24000 and add up the resulting volumes. If this doesn't equal the volume found in the experiment then the equation is incorrect.
Since you are heating then you may have to use the formula pv = nRT but you will need to know the pressure, moles and temperature to use this.
Hope this helps!