The specs do not mention which SODIMM slots to use or a specific memory capacity arrangement. But I would put the 4 GB in slot A and the 2 GB in Slot B. This video may help as well.
I have two latitude E5410 I have been able to rebuild one with windows 10 but needed 8gb ram.  The second I onlt have 2gb ram for both banks, I can get the windows on But as soon as I turn the internet on I loose the screen.  The windows is still running I can hear the Cortina giving instruction   Can I put one 4gb ram and one 2gb ram in to allow the unit to function.  If so which bank should the 4gb go in and which bank should the 2gb go in
ram distribution