Fix #672: Update fraction error message.

[rt4914]

Explanation

To keep parity between Android and web, an error validation in the fraction input interaction that was present in the android version but not in the web, is being added by #8671.
During this addition, it was suggested by @aks681 that the error message should be changed to 'None of the numbers in the fraction should have more than 7 digits' instead of 'None of the numbers of the fraction should be larger than 7 digits.'.

Checklist

• The PR title starts with "Fix #bugnum: ", followed by a short, clear summary of the changes. (If this PR fixes part of an issue, prefix the title with "Fix part of #bugnum: ...".)
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[veena14cs]

LGTM.