Seaward ClareHAL - Manual (Page 106)

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For PWR tests digit 3 also specifies part of the loops index value.
Characters in columns C0, C1, C2, C3, and C4 add 0, 1, 2, 3, 4
respectively to the loops index value. See the explanation of digit 11 for
HI-POT and EBOND tests for the settings applicable to each loop index
and an explanation of loop functionality.
Your HAL tester