You can feed multiple fruits after the first one sets the timer and it DOESNT reset the timer within those 6 hours. You just need to get the right amount of 'has started growing new feathers message.'

The original spreadsheet linked above is NOT accurate, as that was done under the assumption that x amount of fruits gives a certain colour, but it's since been realised that the growing new feathers message is the key. That spreadsheet will only work if you got the same amount of messages that the person who gave that 'recipe' got from feeding those fruits.