More details about the dimensions:

The seat post minimum mark is about 100mm, while the shim is about 50mm. The top tube is about 75mm below the top of the seat tube. So, a seat post by itself would be past the top tube joint, while the shim ends half-way along the joint.

Some time ago someone reported a broken seat tube - it was broken off right at the top of joint of the top tube. It was caused by an insufficiently inserted seat post - the guy had just an inch-and-a-half inserted. The ensuing discussion had it clear from the experts that it is not about the seat post, but about trashing the frame that the seat post has to be inserted deep enough. I can't find that thread, it had some photos also.