Case 1: NEHGS/AmericanAncestors.org:
AmericanAncestors.org (NEHGS)'s database Massachusetts: Vital Records, 1841-1910 is available to browse as well as search. Choose the Browse box at the right-hand side of the page, and enter 588 in the box for Volume and 115 in the box for Page and hit the Browse button.
First let's take a look at the citation to see what we are viewing:
Massachusetts: Vital Records, 1841-1910. (From original records held
by the Massachusetts Archives. Online database: AmericanAncestors.org,
New England Historic Genealogical Society, 2004.)
After hitting the browse button, you can choose whether you want to see a transcript or an image by choosing the appropriate tab. It's always best to view the original image when that is available.
You can see that the town records are from the town of Sharon (Norfolk County), which is the town you were looking for. The page number 115 is printed in the top right corner.
Case 2: FamilySearch
The image of register page 115 showing records from the town of Holyoke shown in the previous answer is from Volume 587. Marriages registered in the town of Sharon, Volume 588 page 115, are on Film # 004329362 image 845 (of 1116).
You can cross-check this by scrolling back to the divider between the Volumes (around image 728):
My experience is that FamilySearch puts explicit item numbers in the Film Notes when the multiple items are from different collections. When the Film Notes show two volumes from the same record set on the same roll, they expect the user to understand that the earlier volume is the first on the roll. For cases like this, where the start of a new volume is near the end of a roll, it's often easier to start at the end of the roll and browse backwards to get to the page you want to make sure you are in the correct volume.
In all cases, look carefully at the register page to see if the page tells you where the marriage actually took place, since the town listed in the header is only where the event was registered. Marriages in Massachusetts can be recorded in up to three different towns (groom's residence, bride's residence, and the marriage location). If the header is cut off and you don't see a town name, the name of the clergyman can be a clue as to where the wedding took place.