'/worldborder set' allows small decimal numbers but does not display them correctly in chat

When you use values for the /worldborder set command that change the second decimal place, the command feedback says it changed the worldborder but only displays one decimal place.

How to reproduce

1. /worldborder center ~ ~
2. /worldborder set 11
3. Try walking through the worldborder (it won't work)
4. /worldborder set 11.01
5. Try walking through the worldborder (it works even thought it said that size is still 11):

   [Client thread/INFO]: [CHAT] Set world border to 11,0 blocks wide (from 11,0 blocks)