The puzzles about variance reduction of Importance and/or weight window?

I learn biasing from /examples/extend/biasing/B01, here i have a question about this example:
from the run result:
Volume | Tr.Entering | Population | Collisions | CollWGT | NumWGTedE | FluxWGTedE | Av.Tr.WGT | SL | SLW | SLW_v | SLWE | SLWE_v |
cell_00 | 16 | 57 | 16 | 16 | 0.00548738 | 2.2649 | 1 | 2230.9 | 2230.9 | 36430.6 | 5052.77 | 199.908 |
cell_01 | 60 | 78 | 218 | 218 | 0.0209288 | 4.39953 | 1 | 10004.1 | 10004.1 | 59377.2 | 44013.5 | 1242.69 |
cell_02 | 80 | 116 | 503 | 251.5 | 0.0081848 | 2.5228 | 0.5 | 19395.1 | 9697.54 | 99064.8 | 24465 | 810.826 |
cell_03 | 112 | 165 | 905 | 226.25 | 0.00614563 | 2.02231 | 0.25 | 28804.6 | 7201.15 | 80816.9 | 14563 | 496.671 |
cell_04 | 124 | 203 | 1174 | 146.75 | 0.00597167 | 1.58526 | 0.125 | 37558.2 | 4694.77 | 47084.5 | 7442.43 | 281.173 |
cell_05 | 136 | 194 | 1121 | 70.0625 | 0.00301685 | 1.37131 | 0.0625 | 34759.9 | 2172.5 | 38833.6 | 2979.17 | 117.155 |
cell_06 | 136 | 196 | 1237 | 38.6562 | 0.00401678 | 1.32717 | 0.03125 | 38118.7 | 1191.21 | 15956 | 1580.93 | 64.0918 |
cell_07 | 134 | 200 | 1228 | 19.1875 | 0.00433664 | 1.42269 | 0.015625 | 38026.9 | 594.171 | 8123.83 | 845.318 | 35.2301 |
cell_08 | 122 | 174 | 1095 | 8.55469 | 0.00352978 | 1.07046 | 0.0078125 | 33414.8 | 261.053 | 3609.92 | 279.448 | 12.7422 |
cell_09 | 114 | 164 | 1216 | 4.75 | 0.00250771 | 0.899316 | 0.00390625 | 33768.8 | 131.909 | 2140.03 | 118.628 | 5.36658 |
cell_10 | 105 | 145 | 996 | 1.94531 | 0.00290177 | 0.929669 | 0.00195312 | 29918.8 | 58.4351 | 889.021 | 54.3253 | 2.57973 |
cell_11 | 82 | 127 | 888 | 0.867188 | 0.00270636 | 0.959093 | 0.000976562 | 25006 | 24.4199 | 402.644 | 23.421 | 1.0897 |
cell_12 | 66 | 105 | 684 | 0.333984 | 0.00294778 | 0.929921 | 0.000488281 | 19748.7 | 9.6429 | 133.18 | 8.96713 | 0.392586 |
cell_13 | 78 | 111 | 768 | 0.1875 | 0.00248326 | 1.06956 | 0.000244141 | 22842.1 | 5.57668 | 100.157 | 5.96456 | 0.248716 |
cell_14 | 70 | 102 | 779 | 0.0950928 | 0.0036858 | 0.854578 | 0.00012207 | 21047.3 | 2.56925 | 28.409 | 2.19562 | 0.10471 |
cell_15 | 58 | 87 | 526 | 0.0321045 | 0.00235877 | 0.857117 | 6.10352e-05 | 16032.1 | 0.97852 | 17.9904 | 0.838706 | 0.0424351 |
cell_16 | 50 | 73 | 557 | 0.0169983 | 0.00498093 | 0.906372 | 3.05176e-05 | 17327.3 | 0.528788 | 4.88971 | 0.479279 | 0.0243553 |
cell_17 | 49 | 65 | 522 | 0.00796509 | 0.00274234 | 0.535091 | 1.52588e-05 | 13829.1 | 0.211016 | 2.66992 | 0.112913 | 0.00732183 |
cell_18 | 28 | 48 | 301 | 0.00229645 | 0.000925889 | 0.385463 | 7.62939e-06 | 7925.2 | 0.0604645 | 1.68507 | 0.0233068 | 0.00156019 |
cell_19 | 14 | 14 | 14 | 0.000106812 | 0.00366572 | 0.543045 | 7.62939e-06 | 1936.6 | 0.0147751 | 0.138901 | 0.00802355 | 0.000509174
what is the mean of the arguments:
"Tr.Entering | Population | Collisions | Coll
WGT | NumWGTedE | FluxWGTedE | Av.Tr.WGT | SL | SLW | SLW_v | SLWE | SLWE_v "