safari tabs won't stay closed after I X them out

I was having this problem for a month... I have 48 tabs open in Safari, I close 20 of them... I close Safari and then go back in, and the same 48 tabs are still active.... do this!!!!... after you close all the tabs you want, go to the bottom of the tabs and hit the down arrow of the tabs you have open... it lists groups, but all I did was re-check my new tabs of 20, and click done... it worked! all my closed tabs stayed closed.