When viewing a card you could see it at the bottom of the page. In a slideshow I'm not sure. The column that has that is Domo's default _BATCH_LAST_RUN_ but you can't use it as a summary number. I'm assuming you're talking about a publication when you saw slideshow so in that case I don't have a slick answer for you

Assuming you have the timestamp in your data you can put it in the summary number through use of the concat() function in a beast mode.  Screenshot above.  One thing to note is that you lose all formatting using the concat() function so you will see additional functions to format the numeric value with a comma.

Beastmode function below.

case
when sum(`daily_admissions`)>99999 then concat(left(sum(`daily_admissions`),3),',',right(sum(`daily_admissions`),length(sum(`daily_admissions`))-3),' Skier Visits<br><div style=''font-size:12px''>Last Updated: ',DATE_FORMAT(max(`lastupdated`), '%m/%d/%y %h:%i %p'),'</div>')
when sum(`daily_admissions`)>9999 then concat(left(sum(`daily_admissions`),2),',',right(sum(`daily_admissions`),length(sum(`daily_admissions`))-2),' Skier Visits<br><div style=''font-size:12px''>Last Updated: ',DATE_FORMAT(max(`lastupdated`), '%m/%d/%y %h:%i %p'),'</div>')
when sum(`daily_admissions`)>999 then concat(left(sum(`daily_admissions`),1),',',right(sum(`daily_admissions`),length(sum(`daily_admissions`))-1),' Skier Visits<br><div style=''font-size:12px''>Last Updated: ',DATE_FORMAT(max(`lastupdated`), '%m/%d/%y %h:%i %p'),'</div>')
else concat(sum(`daily_admissions`),' Skier Visits <br><div style=''font-size:12px''>Last Updated: ',DATE_FORMAT(max(`lastupdated`), '%m/%d/%y %h:%i %p'),'</div>')
end