The difference between shared plans and allotted data amount plans is the amount of data able to be used by one line on the family plan.
With a shared data plan, if you have 4 lines and a 6 GB plan then each line shares those 6 GB. One line could use 3 GBs of data, whereas another 3 lines each only use 1 GB. This helps balance out the amount of data going unused on a plan.
With an allotted data plan, if you have 4 lines and a 6 GB plan then each line only gets 1.5 GB of data. 1.5 GB of data is 6 GB divided into 4 lines. Once you use your allotted amount per line your data will either be cut off or slowed down.
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From these results look closely while scrolling down the page to see if the plan says shared across all lines or if there is a number that is half of the data amount. The ones that say shared across all lines are obviously the shared plans the ones that state how much data each line are the allotted amount plans.