Do I qualify or will I need transit or tourist L type

I arrive in Beijing at 22.30 on a Saturday. I will leave Beijing for Irkutsk on the Trans Siberian at 11.22 a.m. on the Wednesday. By my calculation this is 84 not 72 hours but it seems ridiculous that I need to get a visa just for 12 hours. I'm assuming getting through luggage collection and customs might take a while, so this might push my arrival over to the Sunday morning

Are you able to clarify for me whether I will need a regular L type or if I would qualify for the 72 hour. Also what constitutes "the administrative area of the transit city"?

Regards,
Anne