how to add more than one sub-type?

Hi. I am using the type plugin, which is great.

I added type, and one subtype for each type successfully.

However, if I added more than one subtype under each type, when user sign up for a blog, only the last subtype of each type pops up.

$blog_subtypes[0] = ‘Subtype1’;

$blog_subtypes[0] = ‘subtype1’;

$blog_subtypes[0] = ‘type1’;

$blog_subtypes[0] = ”;

If I wanna add another subtype under type1, how can make it?

Thanks.

Ning