The phrase "an even smaller amount" is correct and usable in written English.
It can be used when comparing quantities, particularly when indicating a reduction in size or quantity relative to something else.
Example: "After the first round of cuts, we were left with an even smaller amount of resources to allocate for the project."
Alternatives: "a lesser amount" or "a reduced quantity".
That first round of ads had an even smaller amount of money behind it.
The bureau estimates that inventories shrank by an even smaller amount in the first quarter — although it won't get equally accurate data until next July — but the effect of the revision was to reduce the difference between the two quarters, and thus to reduce the rate of growth.
A hard sphere mixture is subject to an even smaller amount of subadiabatic temperature increase than a single-component hard sphere fluid, only about 10 K.
Now that same team has detected a second, completely separate gravitational wave that stretched the LIGO legs an even smaller amount than the first wave.
Claustrophobia, the "irrational fear of being shut in; fear of enclosed spaces, such as elevators and tunnels," is believed to affect roughly five to seven percent of the world's population, with an even smaller amount actually seeking treatment.
Addition of AgNO3 to 1 in the presence of acid caused this peak to shift by an even smaller amount to −65.8 ppm.
So what do we do when told it's possible to change our futures by exercising an even small amount of effort in the present?
Spoon an even, small amount into each bowl.
As a consequence, even small amounts of fuel can form flammable clouds, and partial volume deflagrations may occur.
Observational studies to date have reported an association between even small amounts of residual renal function and improved patient survival and quality of life.
The reaction is caused by salicylate intolerance and is not a true allergy, but rather an inability to metabolize even small amounts of aspirin, resulting in an overdose.
