Glow will not let me say the end of AF

Sh
My AF ended today but glow will not let me shorten the period it only allows me to make it longer. It does this every month my Af sometimes only goes 3 days n other times 5 but glow always puts it 5 n never lets me change it when its 3 how am I suppose to get accurate information if it won't let me give accurate information. Please fix