How to displaying advert after first post, 15th post and 29th post?

[RyanFabbro]

im not 100% on this sombody correct me if im wrong, i know for a fact to get it to display after the first post you would go into postbit / postbit legacy and at the very bottom add

<if condition="$post[postcount] == 1">
your ad code here
</if>

so i can only assume what your looking for would be the same steps but use

<if condition="$post[postcount] == 1,15,29">
ad code
</if>

again im not 100% on that, and dont relly want to make 29 tests post to check it lol sry but it seems right =)