edges_found and edges_covered mismatch

Hi all,

I am using aflplusplus and a custom afl++ fuzzer to do the experiment.
During fuzzbench experiment, afl++ will generate plot_data record:
```# relative_time, cycles_done, cur_item, corpus_count, pending_total, pending_favs, map_size, saved_crashes, saved_hangs, max_depth, execs_per_sec, total_execs, edges_found```
Fuzzbench will use snapshot to evaluate the fuzzer performance recording: ```,git_hash,experiment_filestore,experiment,fuzzer,benchmark,time_started,time_ended,trial_id,time,edges_covered,fuzzer_stats,crash_key,bugs_covered```

And I found in the same experiment, edges_found is less than edges_covered. Any idea why?
Additionally, the edges_found in custom_aflpp is higher than edges_found in aflpp, but edges_covered in custom_aflpp is less than edges_found.
Here is the shortcut of raw data:
plot_data of custom_aflpp:

Relative Time | Cycles Done | Current Item | Corpus Count | Pending Total | Pending Favs | Map Size | Saved Crashes | Saved Hangs | Max Depth | Executions Per Second | Total Executions | Edges Found
-- | -- | -- | -- | -- | -- | -- | -- | -- | -- | -- | -- | --
50398 | 23 | 128 | 1699 | 232 | 0 | 27.35% | 0 | 0 | 13 | 4849.04 | 304726213 | 1588
50403 | 23 | 107 | 1699 | 232 | 0 | 27.35% | 0 | 0 | 13 | 5302.55 | 304753210 | 1588
50408 | 23 | 1036 | 1699 | 232 | 0 | 27.35% | 0 | 0 | 13 | 5249.57 | 304779127 | 1588
50413 | 23 | 1093 | 1699 | 232 | 0 | 27.35% | 0 | 0 | 13 | 5162.56 | 304807198 | 1588
50418 | 23 | 107 | 1699 | 232 | 0 | 27.35% | 0 | 0 | 13 | 4887.70 | 304831321 | 1588

plot_data of aflpp_baseline:

Relative Time | Cycles Done | Current Item | Corpus Count | Pending Total | Pending Favs | Map Size | Saved Crashes | Saved Hangs | Max Depth | Executions Per Second | Total Executions | Edges Found
-- | -- | -- | -- | -- | -- | -- | -- | -- | -- | -- | -- | --
56686 | 611 | 1673 | 1913 | 16 | 0 | 26.73% | 0 | 0 | 15 | 16005.00 | 896729564 | 1552
56691 | 611 | 821 | 1913 | 16 | 0 | 26.73% | 0 | 0 | 15 | 15045.84 | 896808391 | 1552
56696 | 611 | 366 | 1913 | 16 | 0 | 26.73% | 0 | 0 | 15 | 16217.05 | 896887749 | 1552
56701 | 611 | 1473 | 1913 | 16 | 0 | 26.73% | 0 | 0 | 15 | 16599.39 | 896977824 | 1552

Edge covered of custom_aflpp:
Relative time| Trial_id | edge_covered
-- | -- | --
45900|28|1978
46800|28|1978
47700|28|1978
48600|28|1978
49500|28|1978

Edge covered of aflpp_baseline:
Relative time| Trial_id | edge_covered
-- | -- | --
54900|13|2000
55800|13|2000
56700|13|2000
57600|13|2000