Hi @JocelynkP I've been thinking about your question and had a couple of thoughts here.
First - if it's only lead ads coming in - then after the first 100 signups won't the ad be changed? For how long would you run the ad? I can imagine that after the first 100 signups the ad is less relevant or becomes inaccurate?
Now as to solving this issue, you could use Zapier to connect fb lead ads and klaviyo and have a counter (using storage) that auto increments a number and add this as a metric or profile property. Then use the trigger or conditional split to filter based on this property. More info on adding a counter https://help.zapier.com/hc/en-us/articles/8496197365389. Probably doing this manually, just stopping the ad of flow whenever you reach that limit could be an easier solution
Anyway, I hope this helps.
Omar Lovert // Polaris Growth // Klaviyo Master Platinum Partner