In the reduplicated Aorist of the Causative, ī is substituted optionally for the vowel of the reduplicate in gaṇ,
As अजीगणत् or अजगणत् ॥ गण is a root which ends in अ, and this अ being elided by 6.4.48 before the Causative णि, the rule 7.4.93, does not apply to it, because there is an ak-lopa here, so in the other alternative, it has its natural अ ॥,