According to multiple sources on Scrum development, there are many accepted ways to define story points.

From Scrum Methodology

Common estimating methods include t-shirt sizes (S, M, L, and too big), powers of 2 (1, 2, 4, 8), the Fibonacci sequence (1, 2, 3, 5, 8, etc.), or simply small vs. needs-to-be-split

That leads to two suggestions:

#1
Additional methods of defining story points should be implemented in Agile, allowing Project Administrators to choose the best way to apply story points on their issues.

#2
There's no Scrum documentation referring to story points as decimal values, therefore JIRA accepts the input of such values.