I cannot think of a single legitimate reason for this capability to be found in a voting machine.
First off, I am disturbed by other things revealed in the video, mainly access to tabulators and remote access to voting machines, if indeed that is what is being shown.
Second, if it can be verified that it’s possible to change live voting machines and/or tabulators to somehow tamper with the results, that also is extremely disturbing.
With all that said, decimals themselves don’t need to alarm anyone.
There are a limited number of numeric data types in database software, especially in the most popular foundation database products. Microsoft SQL and Oracle’s MySQL are by far the most popular ones, even to the point that the latter one (being very scalable and open-source) provides the base for practically all social media, like Facebook and Twitter.
There is an integer data type, but there’s a problem with it being used for elections - mainly that it cannot contain a number larger than 5 digits.
Double precision numeric datatypes, however, can hold a huge amount of digits. It can represent every number used by mankind. There are only two drawbacks to it - the amount of computer memory and hard disk space they take up (really not much now that we’re in the gigabytes of data, but it was a big problem in the past), and in regard to elections, they contain places for decimals even when they’re not being utilized (i.e., all zeros).
Hence the word “double” being shown in the video. It means “double precision”.
https://en.wikipedia.org/wiki/Double-precision_floating-point_format