Size problems on Etcher

I’m trying to move a Raspbian Stretch image to a new 16gb card - the old card is lost - but its a different make from the one I backed up; the ‘real’ size is down from 15.9GB to 15.7GB, and Etcher reports ‘not enough space’.

I realise it’s probably a Raspbian issue, but since Etcher will happily create a 32GB image from a 16GB backup, I’m hoping there may be a way to reduce the image size just a little bit.

I’m using - I think - version 1.0.0 on a MacBook Pro 13 inch, early 2015 under High Sierra. Would upgrading Etcher help?

(Because I’ve no longer got the old card I can’t just boot it and use the Raspbian card copier. I’ve tried Etching a 32GB image, booting it and creating a 16GB version on the RasPi, but it seems to go wrong when I update the distro.)