Amps, real arithmetic vs Itey arithmetic

OK, WTF!

Bike wouldnt start, per suggestion here checked fuses, found 15A/position B fuse popped.
Bunged in a 15 spare. Starts. I have some extras in the jeep so I go grab a 20A, swap it in,
bam, blows the 20A fuse. I stick the 15A back in, and it runs, doesnt blow fuse...yet.

Is it just me, or does this only make sense in Mandello Del Lario?

Should I just carry a baggie full, assume one per start? I know, I'll make a key fob out of a tupperware and fill it with fuses. I'll mount a tupperware on the bars, just in case.

Folks, the connectors, at least the ones I can eyeball, are all clean. Indoor bike for the most part.
Last ride was in rain.

Seriously,

!@#$%^&*()(*&^%$#@!@#$%^&*()_(*&^%$#@!@#$%^&*()_(*&^%$#@#$%^&*()_)(*&^%$#@!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

I can tell you as an electrical engineer that fuses are not precise devices.  Plus each type of fuse has a blow curve and it is quite possible that a 20A fuse of one type will blow before a 15A fuse of another.  If you were to overlay the two blow curves they would cross each other in this case.  I don't know in your case if the fuses are of the same type or not but it is something to consider.
Good luck,
tod