Mathematically given that 30% is fast acting your would need 14u to give 4u of rapid and 10u of background if you multiply this up for each meal (assuming 3) you would daily take 12u rapid and 30u background per day from a total of 42u.
This MIGHT help you work out what you need, but I would agree with the other posters, whilst this is better than NO insulin you really should contact GP/DSN for a repeat script and get the right sort for your own calculations!
My maths is only approx. as it does not work out without fractions! And I find as a novomix 30 user that even after shaking vigorously to re-mix the two types every time it doesn't always seem to be the same!