This page provides you a quick summary on what is AQLEN and DQLEN in ESXi.
AQLEN is the adaptor queue length. This should be derived from storage adaptor queue depth, which is the maximum commands which can be in the queue waiting for process.
DQLEN is the device queue length. This should be derived from storage device(usually drives) queue depth, which is the maximum commands which can be in the queue waiting for process.