Why is the standard deduction on my state of minnesota tax return 30,700 but my federal standard deduction is 30,750?

This is correct.

The Minnesota standard deduction $50 less than the Federal standard deduction.

The Federal Standard deduction is $30,750 for a joint return couple with one spouse aged 65 or over.

The Minnesota standard deduction for the same couple is $30,700.

Please read this IRS document and this Minnesota Revenue document.