The tests for core antigen and PCR RNA are only roughly comparable so some of the difference will simply be due to that.
Although PCR results get reported like 1,234,567 suggesting great accuracy depending on the test the accuracy is nothing like that.
Different tests report different results, and even the same test, repeated on the same sample will have a standard deviation of something like 0.1-0.2 log. While 0.2 log might not sound like much in statistical terms 95% of results appear within 2 standard deviations of the mean. In English if the standard deviation is 0.2 log and the result is log 6 (ie 1 million) then we might see any of the following results for a retest of the same sample using the same test
2 SD below = log 5.6 = 398,000
1 SD below = log 5.8 = 763,000
0 SD = log 6 = 1,000,000
1 SD above = log 6.2 = 1,584,000
2 SD above = log 6.4 = 2,515,000
Add that to the observed reality that viral load goes up and down over time quite naturally and there is no significance to this other than to say you definitely have Hep C and the viral load is relatively low (the average load is 1-3 million)