Dell PowerEdge T30 - memory

[PaulStat]

I'm about to buy myself the above server for home use, the manual (https://topics-cdn.dell.com/pdf/poweredge-t30_owners-manual_en-us.pdf) says the following

The PowerEdge T30 system supports up to four 2133 MT/s (ECC) and 2400 MT/s (Non-ECC), single rank or dual rank UDIMMs.

By default it ships with a single 8GB DDR4 2133MHz module, I plan to buy an additional 16GB module running at 2400MHz (nothing special just a crucial). Am I right in thinking that until all 4 DIMM slots have 2400 modules then it'll run at 2133MHz?