From Wikipedia:

Nielsen SoundScan began tracking sales data for Billboard on March 1, 1991 and the first Hot 100 chart to debut with the system was released on November 30, 1991. Previously, Billboard tracked sales by calling stores across the U.S. and asking about sales; a method that was inherently error-prone and open to outright fraud.

The Recording Industry Association of America also tracks sales (or more accurately, shipments less potential returns) on a long-term basis through the RIAA certification system; it has never used either Nielsen SoundScan or the store-calling method.

Live From Radio City Music Hall (album) - Columbia - November 6, 1992

98,687

Gently - Angel - March 19, 1996

76,881

Highlights Carnegie Hall Concerts - Telarc - August 15, 1989

71,602

Liza With a 'Z' - Columbia - August 16, 1988
(no report on the March 2006 Reissue, unless this number includes both versions)

41,128

Live From Radio City Music Hall (video - VHS) - Columbia - November 6, 1992
(This Video was certified GOLD, which represents sales of between 500,000 and one million copies sold .... So, you can see just how incorrect these figures can be with SoundScan)

40,960

Results - Epic - October 13, 1989

38,748

Liza's Back - J Records - October 29, 2002

28,345

At Carnegie Hall (2-CD set)   - Telarc - 1987

24,390

Minnelli on Minnelli - Angel - February 29, 2000

20,680

16 Biggest Hits - Sony - July 18, 2000

12,764

Ultimate Collection - Hip-O - November 6, 2001

10,278

Day After That (single) - Columbia - November 23, 1993

9,821

Best of Liza Minnelli -- Columbia-Sony - September 14, 2004

6,065

Singer - Columbia - January 25, 1985
(that date is wrong, it was released on CD circa 1988-1989; the number of copies sold is likely wrong also)

4,967

All That Jazz - Sony Special Markets - May 29, 2000

3,324

Maybe This Time - Capitol - February 16, 1988

2,892

Day After That (video) - Columbia - January 4, 1994

1,739

Foursider - A&M - May 20, 1988

1,247

Complete Capitol Collection - DRG - July 25, 2006

1,102

Tropical Nights - DRG - February 12, 2002

1,080

Visible Results (video-VHS) - Columbia - March 9, 1990

790

When It Comes Down To it 1968-1977 - Raven - February 17, 2004

747

Losing My Mind (single) - Sony - August 21, 1989
(Again you can see how these numbers would be off : It's not possible that this smash hit single for Liza could have sold only 58 copies)

58