AWS Kinesis write throughput has no data, but there are data in total incoming request

Hi I'm using Kinesis to handle data streaming.

I can successfully send data to Kinesis and pull data from Kinesis, everything is good.

But when i check the "monitoring" of Kinesis, i see no data for write throughput, but there are data for total incoming request (in attached screenshot). Since i can successfully pull data from Kinesis, i assume there must be some writing throughput, how come no writing throughput in the monitoring?

Or maybe I misunderstand the term "write throughput" and "incoming request"?

Thank you very much.