Approaching the calculator project, test story #9

Can anyone offer any tips on how I can decompose this problem before I start coding it? I feel like my solutions for the previous javascript projects were a little rushed in that I could have seperated things in smaller components. I have been trying to use react for these projects and also trying to not to use redux as I feel it is a bit excessive.

One part that confuses me is user story #9, where the calculation should handle numbers of any length, when in the calculator provided in the sample, there is a clear limit when a user enters too many numbers. I believe it displays MAX_LIMIT_DIGITS. So how did it pass test #9?

@Siegeprogrammer me for instance I checked out my state screen property, for its length should be <= 21, otherwise i call on a maxDigitException which displays on that screen property of my state, a mesage, by setting the screen property with the setSate(‘Max digit encountered’)… something like that. Because if you don’t do so, the digits will overflow the screen my dear.