What is an improperly zeroed Vernier Caliper?

Care must be taken to insure that the vernier caliper is properly zeroed. (With misuse, it is possible that the vernier will not read zero when the jaws are closed, thus leading to systematic errors.) To correct this, a zero correction must be made. A correction may be either positive or negative. If the first mark on the auxiliary scale lies to the right of the main scale, then the reading is too large and the error is positive. The zero reading is +0.05 cm and should be subtracted from any measurement reading. Similarly, if the first mark on the auxiliary scale lies to the left of the main scale zero-mark, then the error is negative and the correction should be added from the measurement reading.