information for a a raw japanese sweet potato is all over the place. Is the nccdb entry for sweet potato close enough?
For the ones purple on the outside and pale on the inside.
I assume the standard sweet potatoes are the orange ones, so they will be higher in beta carotene than a pale variety.
It's also worth remember that the nutrition of any fruit or veg depends on where it was grown, what season, weather and rainfall, fertilisers, how it's been stored, how long it's been kept etc etc.The piece of food in front of you may be quite different from whatever standard pieces were used to come up with the values.
I was going to suggest pick another variety of purple sweet potato, but the only one I can see in the database is branded and only has 20 nutrients recorded. It's brand it Stokes, and seems to be British. That's probably a better choice than orange though, which will throw you vitamin A out by miles.