2 , ▁Billboard ▁employed ▁updated ▁data ▁capture ▁technology ▁in ▁compiling ▁the ▁chart , ▁using ▁point - of - s ale ▁ret ail ▁information ▁provided ▁by ▁N iel sen ▁Sound Scan , ▁input ▁from ▁radio ▁station ▁air play ▁monitoring ▁provided ▁by ▁Broadcast ▁Data ▁Systems ▁and ▁play lists ▁from ▁small - market ▁systems . ▁ ▁The ▁chart ' s ▁first ▁issue ▁mentions ▁that ▁a ▁rank ▁position ▁indicates ▁" relative ▁potential ▁to ▁ear n ▁an ▁early ▁listing ▁on ▁the ▁Hot ▁ 1 0 0 " ▁and ▁records ▁were ▁ranked ▁starting ▁with ▁# 1 . ▁From ▁August ▁ 2 8 , ▁ 1 9 6 1 , ▁to ▁August ▁ 2 4 , ▁ 1 9 8 5 , ▁the ▁chart ▁positions ▁were ▁number ed ▁starting ▁with ▁number ▁ 1 0 1 . ▁Songs ▁that ▁have ▁already ▁appeared ▁on ▁the ▁Hot ▁ 1 0 0 ▁are ▁not ▁included ▁in ▁the ▁B ub bling ▁Under ▁chart ▁as ▁they ▁exit ▁the ▁charts , ▁but ▁may ▁re - enter ▁the ▁B ub bling ▁Under ▁chart ▁at ▁a ▁later ▁date . ▁ ▁Ch anges ▁and ▁alter ations ▁Over ▁the ▁years , ▁the ▁chart ▁would ▁under go ▁several ▁changes ▁and ▁alter ations . ▁In ▁the ▁ 1 9 6 0 s , ▁the ▁chart ▁included ▁as ▁many ▁as ▁ 3 5 ▁sl ots ; ▁on ▁two ▁rare ▁occasions ▁in ▁ 1 9 6 3 ▁and ▁ 1 9 6 8 , ▁the ▁chart ▁contained ▁ 3 6 ▁sl ots . ▁By ▁the ▁ 1 9 8 0 s , ▁the ▁chart ▁contained