I am staking 12.000 clams from desktop wallet. Time expected to earn 1 clam is 1 hour (says wallet) But I am not getting more than 5-8 each day.
Is that ok.
Not sure where that calculation comes from but it isn't correct.
You are staking 12k claims. The reward per staked block is 1 clam. If you were to get one block every hour that would be 1/60 of the total, so by simple math the the network total staked would be 720k. That's off by half or more.