i get a 620 on the first powerperp test, 670 on the second one, 590 on kplan test...
then i reach on the real gmat and i get 550 ( 39Q 24V)
why? the only reason i found is that the monitor was too close to my face (about 20cm) and i have no enough space on the table to do the calc on the math part... (about 15Cm from the monitor to the end of the table)
they say that all centers must be equal in order to ensure that everyone is test under the same conditions...
Did you have the same problem? how do you fight with it?