If handbags were put/kept on the worktop a box of loose bullets wouldn't have been missed. Was it June's handbag which was photographed there beside the box ?
The whole argument is based on an assumption that Sheila would notice the bullets and later remember them being there prior to first having to reload.
The defence narrative is simple. After shooting eight bullets into June and Nevill she then goes to where she knows the ammo is kept and loads five bullets. Realising soon after there is another source of ammunition on the kitchen worktop.
A prosecutions narrative is actually more problematic. Since only five bullets were taken from the cupboard and 20 from the kitchen table. Hence the killer used 20 bullets from the kitchen. Why then would Jeremy take five from the cupboard? He would undoubtedly know about the ones on the kitchen table since he put them there.
