Go to the BP_SmartAIComponent and create a new variable called MaxHealth and set it to a Integer. Then set the Default value to 100 and tick on Instance Editable and compile.

Add the highlighted nodes shown in the image below, location at the top of the image.

Now if your AI has a health value above 100 you will also need to set the MaxHealth variable you just created in its SmartAIComponent inside the AI’s character blueprint to whatever your AI’s max health will be.