Compounds that have the same molecular formula but different chemical structures are called isomers. Depending on what types of differences there are between the structures, it is possible to classify isomers into various sub-types.
The Limit. You can follow up to 7,500 users before receiving the aforementioned error. Instagram invoked this limit to reduce spam in their system and keep users in compliance of their Community Guidelines. However, some users can follow more than 7,500 users if they did so before Instagram imposed the limit. Some Instagram users also claim there's an hourly or daily limit to the number of new followers you can acquire, but Instagram has not confirmed such restrictions.
This means if you have 1,819 followers you can break through the 2,000 limit. Below 1,819 you are capped at following 2,000 people. Above 1,819 you can follow this number +10% (or 182). At 1,819+10% this means you can follow 2,001 people and you have just broken the 2,000 limit- hurray! This (as Rob Brown mentions on this post) means for every 10 people that follow you, you can follow 11.