The Maximum Number of Iterations is a Restoration Parameter of the Huygens Software that puts a limit to the iterative deconvolution.

Maximum Likelihood Estimation-based deconvolution methods use an iterative process that never stops if no stopping criterion is given. This stopping criterion can simply be a maximum number of iterations at which the process will stop. This value depends on the desired final quality of your image. For an initial run you can leave the value at its default. To achieve the best result you can increase this value.

Another limit is established by the Quality Change Threshold parameter.