555 servo controller "modulation input"?
The modulation input can be used to raise the charging potential for the capacitor. This means if you take pin 5 above where it normally sits (two-thirds Vcc from memory) the frequency will reduce if configured as an astable and the time delay will increase if used as a monostable.

You can round any component value to any other but, whether it will work as you require that's a different story. Show a circuit if you want a more useful answer.