On the brymen BM867, the printed cat4 1000V rating on the multimeter is only for the V/ohm++ input. The manual clearly states that the A/mA inputs is rated for cat4 600V AC/300V DC. That's why the fuses are not rated 1000V. Many of the brymen multimeter's have different cat ratings for the A/mA input and the V/ohm++ input.

From the manuals:

BM867 Terminals (to COM) measurement category:

V : Category IV 1000 Volts AC & DC

mA?A : Category IV 600 Volts AC and 300 Volts DC

A : Category IV 600 Volts AC and 300 Volts DC

BM869 Terminals (to COM) measurement category:

V / mA?A / A : Category IV 1000 Volts AC & DC

BM857 Terminals (to COM) ratings:

V : Category III 1000 Volts AC & DC, and Category IV* 600 Volts AC & DC.

A / mA?A : Category III and Category IV* 500 Volts AC and 300 Volts DC.

BM859CF Terminals (to COM) ratings:

V / A / mA?A : Category III 1000 Volts AC & DC, and Category IV* 600 Volts AC & DC.

TBM811, TBM812 & TBM829 Terminals (to COM) measurement category:

V : Category IV 1000 Volts AC & DC

mA?A : Category IV 600 Volts AC and 300 Volts DC

A : Category IV 600 Volts AC and 300 Volts DC

TBM811XEX, TBM812XEX & TBM525 Terminals (to COM) measurement category:

V / mA?A / A : Category IV 1000 Volts AC & DC

BM250(251,252,255,257) Series:

Terminals (to COM) measurement category:

V : Category II 1000V, CAT III 600V and CAT IV 300V AC & DC.

mA?A : Category III 500Vac and 300Vdc.

A : Category III 600Vac and 300Vdc.

Link to some of the brymen manuals:

http://www.brymen.com/product-html/0000-User/