Hi @ravinesh_mishra
Try the below class in admin theme:
.custom-options .option-box .border input.input-text, .custom-options .option-box .border select.select
{
width:95% !important;
}
or Try with static width
.custom-options .option-box .border input.input-text, .custom-options .option-box .border select.select
{
width:165px !important!;
}
I hope it will help you!