Good question. Here is the text of the law (in Turkish): https://www.resmigazete.gov.tr/eskiler/2020/07/20200731-1.ht...

It says "the social network provider's band width to be reduced by ...%"

I'm not a law expert but my guess is that they will send order letters to the ISP's and the ISP's will act the way they see fit. If Erdogan is not impressed, they will give the CEO's a call to improve the bandwidth reduction. If they don't comply, they will have hard time getting the permits to install cables or win government contracts, so they will comply.

When a website is blocked in Turkey, it's up to ISP's to choose the blocking method. Some ISP's blocks are stronger than others(some simply block DNS and you are not affected if you use GoogleDNS or OpenDNS etc. others block the IP so your only recourse is to use VPN). Also, some websites are more blocked than the others(On the same ISP you can have some websites IP blocked, others DNS only).

Knowing the little governments usually know about tech, I'd say it was a random number chosen by a dice roll, guaranteed to be random.

The rumor is it is the magic number that gives you a good enough page load times as long as there is no video content.