My reading of Griffiths is that Philip is listed as having plot 10 which was a farmhouse, outbuildings and just over 31 acres of land. (To be precise he had 31 acres, 2 roods and 33 perches. So that’s just over 31 and a half acres). There’s no “position 31” in that townland. Have you perhaps got the acreage and plot numbers mixed up?
The 1856 listing shows 16 properties in the townland. However the map that accompanies it only shows 8. So the map isn’t contemporaneous with the 1856 valuation. The map probably dates to the 1870s (that’s when a lot of them were drawn up). So what’s evidently happened between 1856 and the making of the map is that half the properties have been consolidated. (The 1901 census shows just 11 properties in the townland, 2 of which were empty.).
What you would need to do is to look at the Valuation Revision books in the Valuation Office in Dublin. These records take the 1856 valuation forward (right up to the 1920s). If you track plot 10 in the Revision books, you will see what happened to it. (It was presumably combined with another farm).