Gem File Size

Can someone please help me understand how the gem file size calculation is happening in below scenario for the following measure

/aipdom/srpg $ printMeasure -d . -m sr0_prjinv -specs

SPECS FOR MEASURE: SR0_PRJINV
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label:              Store Projected Inventory
type:               2 (real)
baseint:            sku_str_day_
navalue:            0
defagg:             PET
defspread:          PE
allowedaggs:        PET
range:              0:2147483647
refreshable:        true
db:                 data/sr0_prjinv
insertable:         true
basestate:          1
aggstate:           1
stageonly:          false
filename:           sr0_prjinv
loadint:            sku_str_day_
clearint:           ''
loadstokeep:        0
start:              50
width:              8
loadagg:            TOTAL
purgeage:           -1
viewtype:           0
syncwith:           ''
description:        Projected amount of stock that will be in the store at the beginning of day