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Several points:

Signal meter's on TV sets don't directly measure the strength of the signal, they generally measure the quality of the incoming signal by calculating the error rate of the data packets. A low-strength but high quality signal will get a higher score than a strong signal with impairments that cause decoding errors.

The DB4e is designed for UHF. During field trials that I did early last year, I did observe that any VHF reception it exhibited was well off boresight, usually between 40 and 75° off the straight ahead direction. If your angles happen to line up so that La Jolla is in that off-axis direction, the odds of picking up channels 8 & 10 improve.

Be advised that there's nothing special about the CC-7870. It's just an old-style wire-transformer splitter (and not a very good one, at that) with some packaging. You'd do far better to pick a simple splitter with an internal glass strip design.