Hello, The partition I would cut is the OEM partition. I couldn't find clarification on why the partition would have been broken in two, I'm also used to a single System Reserved partition. Removing it should not impact your ability to use the server, and would be the safest to cut. As for why those two partitions are separate, I'm not sure. I suppose you have a few options though. 1) You can cut the OEM partition and that would meet the 4 partition need, 2) you could delete all the partitions and install cleanly.
I've got a Dell PowerEdge T440 running Windows Server 2016 Standard. This server came from Dell with the OEM Windows Server 2016 OS installed. When the OS was installed I guess five partitions were created. This is causing a problem because I am trying to configure Azure Site Recovery (ASR), and ASR only supports disks with four partitions or less. Specifically, I am getting the error code 95412 from ASR during the Enable Replication step of Site Recovery configuration. I need help figuring out how I can reduce the number of partitions from five to four. See the output from Diskpart below. I can't get rid of partitions 1, 3, 4, or 5. That leaves partition 2. Even then, I am not sure I should get rid of partition 2.  Also, if anybody can explain why System and Reserved are separate partitions, I'd love to know the explanation. I am familiar with System Reserved being one partition, not two.  DISKPART> list disk Disk ### Status Size Free Dyn Gpt-------- ------------- ------- ------- --- ---Disk 0 Online 3352 GB 1647 GB *Disk 1 Online 1863 GB 18 MB DISKPART> select disk 0 Disk 0 is now the selected disk. DISKPART> list par Partition ### Type Size Offset------------- ---------------- ------- -------Partition 1 System 650 MB 1024 KBPartition 2 OEM 100 MB 651 MBPartition 3 Reserved 128 MB 751 MBPartition 4 Recovery 3072 MB 879 MBPartition 5 Primary 1700 GB 3951 MB   TL;DR. WS 2016 server came with five partitions from Dell. I need to reduce the number of partitions to four. partitions.
WS 2016 Disk Partition Help