Um, there's no real nice way to say it, so i'm just gonna say it and hope you don't take it personally:
That's a mess.
But, I'd under rate the fuse instead of over rate it.
But half an amp is not really that much of a concern if you're powering off a clean stable supply. I'd be skepitcal of a fuse that has been measured to .5a anywyas.
The do believe they make mini fuses in .5 amp incriments, but I'm not sure about glass fuses. I believe I've seen .5 amp glass fuses a long time ago. BUt that's from memory and I am getting on in years...........