You can refer to the iClass card structure with article here.
Here's an example for iClass Layout in BioStar. Suprema devices require 6 blocks(48 bytes) for CIS index and then write templates after that. When you write 4 templates in 16K/2 (Template size : 382 bytes - 47.75 blocks)
When you write 2 templates in 16K/16 (Template size : 382 bytes - 47.75 blocks)