The ones created during installation appear to be automatic storage tablespaces - the container names are standard ones (using a specific format).
You are creating non-automatic dms tablespaces - and you have the choice to name the container ... if you want it to be called container2.lrg or container2.LRG or container2.xyz, mention it in the create tablespace statement.
Code:
db2 "CREATE LARGE TABLESPACE tablespace3 MANAGED BY DATABASE USING (file '/db2/db2rep/data1/container33.LRG' 10000)"