Too much cayenne chilli pepper
There are two traditional ways to reduce the hotness of excess chilli.

First, excessive spicy taste is can be neutralized by adding appropriate filler/absorbent ingredients to the mixture. Fresh coconut shreds are commonly used to absorb the excess chilli in chutneys.

Second, you can add sweet and/or sour substances to counter the feeling of hotness. Traditional sour additions to chutney can be:


Tamarind (common)
Tomatoes
Lime or lemon
Vinegar


Typical sweet alternatives are:


Honey
Brown sugar


All these additions may change the flavor and shelf life of the chutney, but you can always experiment. If that is not desirable, just add more of the other recipe ingredients to increase the number of servings.