Yeah I had a hen that laid medium eggs and those came in handy for half recipes quite a bit! No chickens for me for at least a year, hence the ducks.You mean like the ones where they ask "how many of 'object type" are in these pictures? Yeah, sometimes those are near impossible.
Of course you need a variety! I have a number of chicken breeds and they lay anywhere from Small to Jumbo. I weigh and mark each egg. If I am making half a recipe that needs 1 egg I use a Small. 1.5X the recipe, use a Large and a Small or maybe a Jumbo. A 50 gram Small and a 70 gram XL is the same as two 60g Large.