You need to initialize count
before using it the first time. (You should probably include an escape as well, to keep from running off the end of the array if you get more data than your code expects.)
count := 1;
while (not EOF(MasterFile)) and (Count <= NoOfRecentScores) do
begin
Read(MasterFile, RecentScores[count];
Inc(Count); // or Count := Count + 1;
end;
Local variables are not initialized in Pascal, meaning that until you assign a value they can contain any random memory content.