The volume of Butter Futures-Cash (Continuous: Current contract in front) is 18.00.
Open interest is the number of contracts held by traders in active positions — they're not closed or expired. For Butter Futures-Cash (Continuous: Current contract in front) this number is 1.72 K. You can use it to track a prevailing market trend and adjust your own strategy: declining open interest for Butter Futures-Cash (Continuous: Current contract in front) shows that traders are closing their positions, which means a weakening trend.