ALT OVERSHOT DURING DESCENT.

Narrative

UPON RECEIVING A DSCNT CLRNC FROM SAT APCH CTL; WE READ BACK OUR CLRNC LIMIT OF 5000'. AS WE WERE PASSING 5100' FOR 5000; APCH CTL ASKED US TO VERIFY OUR ALT. WE READ 'PASSING THROUGH 5100'.' AT THIS TIME; APCH THEN SAID THAT WE WERE ONLY GIVEN A 7000' CLRNC LIMIT. WE THEN TOLD APCH THAT WE HAD UNDERSTOOD THAT WE HAD A 5000' CLRNC LIMIT AND THAT THIS WAS READ BACK TO HIM BY US IN OUR ORIGINAL CLRNC AND WAS NOT CONTRADICTED BY HIM AFTER OUR READ BACK. AS WE HAD PERCEIVED TO HAVE BEEN GIVEN AN ALT AND READ THAT ALT BACK TO A CTLR FOR A CLRNC LIMIT; THE CTLR SHOULD HAVE LISTENED TO VERIFY THE READBACK AND CLRNC LIMIT. SHOULD THIS CLRNC LIMIT HAD BEEN SOMETHING DIFFERENT; AS THAT OF TODAY'S FLT INTO SAT; THE CTLR SHOULD BE ABLE TO VERIFY A DEP FROM THAT WHICH WAS ON HIS SCREEN AND THAT WHICH WE WERE DSNDING TO. IT WAS 1900' BELOW THE CTLR'S GIVEN ALT ON HIS STRIP AND THAT OF WHICH WE WERE DSNDING TO BEFORE HE EVER VERIFIED THE ALT. THIS WAS NOT DONE IN A TIMELY MANNER FOR A VERIFICATION OF OUR READ BACK ALT OF 5000' AND HIS STRIP OF 7000' TO VERIFY THIS DISCREPANCY. ALL THROUGHOUT THIS GIVEN TIME FRAME; THE CTLED FREQ WAS VERY LIGHT--2 AIRPLANES; OF WHICH WE WERE ONE; WAS ALL THAT WERE THE CTLR'S FREQ.