Your application needs to perform one write and one eventually consistent read per second with item sizes of 1 KB on a DynamoDB table:

Number of writes per second = 1
1 WCU is required for each 1 KB of write. So writes required for each item = ceil(1) = 1
Total WCU required  = 1 x 1 = 1;
Similarly, the number of eventually consistent reads per second = 1
1 RCU is required for 1 strongly consistency read. So, the RCU required for 1 eventually consistent read  = .5
1 RCU is required for 4 KB of read. So reads required for each data item = ceil(1/4) = 1
Total RCU required = .5 x 1 = .5.

Even though the required RCU is .5, we still have to set an RCU of 1. This is because you can only set integers greater than 0 for WCU and RCU.