wording of additional instructions

exercises/practice/grains/.docs/instructions.append.md

@@ -4,9 +4,10 @@ According to [the Vim docs][number]:
 
 > Assuming 64 bit numbers are used (see v:numbersize) an unsigned number is truncated to 0x7fffffffffffffff or 9223372036854775807.
 
-That means that Vim cannot express any number `2^63` or greater as an integer.
+In other words, Vimscript cannot express any number `2^63` or greater as an integer.
 
-For this exercise, you will return the values as strings.
-That means you will have to implement a way to do addition on two _string_ operands.
+Some of the tests for this exercise require 64 bit integers which is behond the integer size limitation ov Vimscript.
+Because of this limitation, the results of the calculations are tested against a string which expresses the integer value, rather than expressing the answer as Integer.
+Can you solve this by avoiding numbers that are larger than the language will allow directly?
 
 [number]: https://vimhelp.org/eval.txt.html#expr-number