Hello,
I hope you are doing well, for the SG300 28P the option of tracking the data transmitted by each port would be under status and statistics -> Interface / Etherlike. There you would be able to see the received statistics and transmit statistics.
Also here is the link to the SG300 administration guide:
http://www.cisco.com/c/dam/en/us/td/docs/switches/lan/csbms/sf30x_sg30x/administration_guide/78-19308-01.pdf
If you have any further questions you can always contact us at: 1-866-606-1866
Have a nice day!