As well as the GUI being incorrect (in terms of putting the wrong statistic against the wrong label), that "large number" is a failure in presentation.
What is being presented appears to be an unsigned 32-bit integer.
What is held in memory is likely to be a signed 32-bit integer, with a value of "-6".
In binary, both look like this: 1111 1111 1111 1111 1111 1111 1111 1010.
It is best ignored. In fact, since our VDSL2 setup uses PTM mode, rather than ATM mode, HEC errors don't apply, and should be ignored anyway.