Estimated cap figure for 2020 is about $177M. Rams have $26.6M in contracts for guys signed for 2020. There are only 12 players under contract for 2020. That explains the huge number.
http://www.spotrac.com/nfl/los-angeles-rams/cap/2020/Compare that list to guys currently under contract
http://www.spotrac.com/nfl/los-angeles-rams/cap/2018/Players not under contract and not counted against the $150M for 2020 with
very rough estimates of cost:
$30M - Goff
$20M - Donald
$15M - A good starting LT
$20M - 4 OL not playing LT
$10M - Gurley
$12M - Brockers
$10M - Talib or a good #2 CB
$15M - Peters
$10M - Joyner
$3M - Greg the Leg
That’s $145M right there. That $150M looks OK, but the Rams have some tough decisions to make over the next two years and need to draft well to get production from cheaper players at position of generally high cost.