PowerEdge T610 Ram configuration question

I have inherited a Dell PowerEdge T610 from a local school, therefore wanted to put it to use elsewhere. However before I do that, my plan was to upgrade the memory to just over 16GB. Currently the server has 8 Gb of RAM comprised of 2 x 4GB inserted into the slot marked A2 and A3, now I have a 16GB compatible RAM module lying around and wanted to make use of it. My question is the following can I simply remove the 4GB RAM from slot A2 and replace it with a 16GB module. Would that be a correct memory configuration?

Sorry but by profession I'm a Security advisor turn Technician (recently) therefore never had the opportunity to upgrade hardware previously.

Thanks in advice.