When number fields are displayed in Jira, and these values exceed 3 digits, there is a convention to use a separator in order to show the difference between thousands, millions, billions, etc. and to represent decimal digits.

Different languages have different languages to represent the decimals and thousands,million etc.The only way to control this is to change your language settings and have your language/region settings adjust this on your behalf. 

Examples:

When you select some language that uses commas to separate thousands and try to enter a number in a number field, you only get the option to use .(dot) to separate decimals.

I would be great if Jira could accept number which include dots to separate thousands and comma to indicate decimals.