Looking at the graph, it seems that training has got quite a bit further to go as the top red line is still sloping downwards and the loss coverage is not diminishing as it should. I'll test the model that this session created, but I think throwing another 1,000 images at the network would be a good idea. I really needed this result to boost my enthusiasm!
It's worth thinking now about the next stage in a bit more detail - how to catch / destroy the slugs? I think a Google questionnaire form might be appropriate with questions to probe people's views on the morals / ethics of killing slugs and the possibility of more 'humane' alternative solutions?