Its the amount of bandwidth that has gone through in 5 minutes , I just changed the bits to mbs to make it clearer of how much traffic has gone through it can be awkward looking at bit rate when using 100mb and 1000mb interfaces and calculating against bits
you can change this value , if you were trying to capture burst traffic you would lower it to load interval 30 under the interface and that would change above , the default as you have above is 5 minutes , longer intervals can hide burst traffic , burst traffic can lead to buffers been flooded and output drops occurring so its handy to be able to lower it for testing reasons but generally don't touch it unless you need to , defaults are there for a reason maybe it leaving it at lower 30 might cause excessive cpu for that process as its calculating more frequently
You can also calculate how many drops per volume of traffic has gone through as well per interface , Cisco recommend no more than 1% , divide the output packets against the total output drop rate x 100
