Your understanding of percentages is right, but let us rephrase the whole thing. To reach an optimum annual staking reward (12% p.a.), you should lock your CRB Tokens for at least 2102401 blocks (1 year). There is no compound interests, when you claim your creditBOND reward, linear interests are calculated and returned, staking period is adjusted accordingly. Whole process is explained in detail in Whitepaper.
Thanks for confirm it! Time to lock for 12 months for 12%!