First a disclaimer.  This is merely an advisory opinion.  Your warrant issue is resolved by your Policy Office, and or the warrant board at your agency.  Meaning different offices work differently and some offer more precise guidance.  The management considerations usually involve workload management and decisions and agency norms and traditions.  How often do you see actions structured at exactly the threshold limit?  Usually there is a reason. As a practical matter, instead of fighting the policy office, understand the policy.   if you and the requirements office want to expedite an action and otherwise allow you to promptly sign it, then structure the action to be clearly within your warrant limit. 

Use your judgement.  Understand that at some point in your career you might be pressured to perform an action that you are not sure about, or comfortable with and believe additional review or oversight is warranted, .if you set or allow the requiring office to set the value at your warrant limit, you will receive the additional review and oversight you  deserve..

To your point, the Simplified Acquisition Threshold (SAT) is the dollar amount below which an agency may purchase property or services using small purchase methods.. The SAT is set by the Federal Acquisition Regulation at 48 CFR Subpart 2.1 (Definitions) and in accordance with 41 U.S.C. 1908. As of the publication of this part, the simplified acquisition threshold is $250,000.00 and is periodically adjusted for inflation.

See also Class Deviation- 2018-O0018, Micro-Purchase Threshold, Simplified Acquisition Threshold, and Special Emergency Procurement Authority. This clause deviation is effective on August 31, 2018, and remains in effect until incorporated into the FARS or DFARS, or until otherwise rescinded. “Simplified acquisition threshold” means $250,000 (41 U.S.C. 134), except for–(1) Acquisitions of supplies or services that, as determined by the head of the agency, are to be used to support a contingency operation; to facilitate defense against or recovery from cyber, nuclear, biological, chemical, or radiological attack; to support a request from the Secretary of State or the Administrator of the United States Agency for International Development to facilitate provision of international disaster assistance pursuant to 22 U.S.C. 2292 et seq.); or to support a response to an emergency, or major disaster (42 U.S.C. 5122), (41 U.S.C. 1903), the term means– (i) $750,000 for any contract to be awarded and performed, or purchase to be made, inside the United States; and (ii) $1.5 million for any contract to be awarded and performed, or purchase to be made, outside the United States; and (2) Acquisitions of supplies or services that, as determined by the head of the agency, are to be used to support a humanitarian or peacekeeping operation (10 U.S.C. 2302), the term means $500,000 for any contract to be awarded and performed, or purchase to be made, outside the United States.