To support what Rubicon said, this is from the DGT site:
With Centaur the ELO rating is not relevant because it adapts its playing strength to your level. In Friendly Mode it will play at your level and in Challenging Mode it will play slightly above your level.
In Expert Mode Centaur does not adapt to your level and it can reach the highest ELO levels. So, depending on your own playing strength and depending on the used playing mode, the ELO rating of DGT Centaur can vary between 300 and 3000.
http://www.digitalgametechnology.com/index.php/support1/frequently-asked-questions/401-chess-computers-faq/dgt-centaur-faq/586-centaur-elo-rating
With the utilization of machine learning for the chess computer AI, you’ll just have to measure its playing strength as follows:
A. 100 elo below yours,
B. 100 elo above yours, or
C. fixed at 3000 elo for your chess studies pleasure.
CHOOSE YOUR WEAPONS . . .