The melting curve and the Cq/Ct-values are essential parameters to evaluate a qPCR assay. It is important to know that
1) the Cq/Ct-values decrease with increasing amount of cDNA
2) given an efficiency of 100 %, each 10-fold dilution step of cDNA mathematically results in an increase of the Cq/Ct-value of 3.32 cycles.
3) in practice an efficiency of exactely 100% will hardly be reached because many independent factors play a role: polymerase, primer design, setup, target sequence, and general PCR conditions.
4) it may happen that the calculation of the efficiency results in a score of more than 100%. This effect is most probably caused by the mathematical method used and does not reflect a problem of the assay.
Most qPCR machines automatically calculate the Cq/Ct-values. If not, please see this list of software and other tools.