error message when enabling plugin

i would really like to test out your plugin, however i’m getting the following message as soon as i enable it.

The plugin generated 32 characters of unexpected output during activation. If you notice “headers already sent” messages, problems with syndication feeds or other issues, try deactivating or removing this plugin.

any ideas on how to resolve??

https://www.ads-software.com/extend/plugins/bbpress-simple-advert-units/