This article will show you the few steps it takes to update the tuning interval for a single piano record. If you are wanting to change your company wide default tuning interval for all future piano records created, read the article HERE
Changing a Piano's Tuning Interval
From within the piano record of the instrument you would like to change, select "Edit" under the piano information box
On the right hand side under details, click the select box under "Tuning Interval" to select a new interval.
Hit save and you're done. Easy peasy!