these guavas are very small. you basically can't - you're left with a rind that's about half the fruit's total weight. the rind is edible, but how much c is in it?
what i ended up doing was separating the rind out and putting it in the bowl, and then sucking the sap off of the part in the middle, before spitting the seeds out. i don't know how worthwhile that was; i couldn't really taste the c, it just had this kind of gross sugary taste. i always like my fruit sour, and never like it sweet. and i don't know if that means that i'm only getting 12 g, or less, of usable fruit from a 25 g guava.
if i'm only supposed to take the part in between out, then these little guavas have almost no usable fruit, at all.
so, this may be a dead end, but i'm going to hope i can find them a tad bigger, next time.
for now, i'm going to double up and enter the data in at 25 g of rind to reflect it. but, i hope i'm underestimating.