Updating Perch 2.5.4 - 2.8.12

The upgrade has gone swimmingly. Just one question.

In the old category link template there's a bit of code that displays number of posts in that category.

<perch:blog id="qty" />

Is there a replacement method for this now as this doesn't seem to work

<perch:category id="qty" />

Cheers, John.