Please understand that these contract mining are not actual mining contracts and are called cloud mining.
You might be better off putting it as simple cloud-mining or simply bitcoin investment and pay 30% short term gain on them
Though, please make sure with a CA or a lawyer
This is correct and best is to consult the CA who have idea about bitcoin. Though now most of the good CA have already know about btc and even it is clear that 30% of the tax needs to be paid on short term profit which is sold within 3 years . So better to let them know your exact contract and they will help you out.