RSAEngine.processBlock的不同byte []大小的原因

What could be the reason/s for different sized byte[] returned from processBlock method in RSAEngine (bcprovjdk16-1.45.jar) class. (127 in one case and 128 in the other on two different machines running the same version of java, [1.7, 64 bit] and using the same public keys for encryption and private keys for decryption and for the same data to be decrypted.What could be the reason/s for different sized