What is the average opt in rate for email lists?

Hey guys,

Recently started my news site and starting to get a good bit of traffic >400 hits a day.

I started an optin landing page type thing earlier today before work.

Came home to these stats:
– 180 unique impressions.
– 5 conversions
– 2.76% conversion rate

Im using a pop up opt in form type thing (once you scroll 15% of the way down the page the pop up box opens).

Is this a good number? Would it be wise to base my future en devours off this number?