The desktop version of the software often can process a higher number than the online. I would suggest you contact the helpdesk and ask it a higher number can be entered in that field then on desktop.
the desktop version goes up to 999,999,999,. however, did you read what the * means? not provided for in the program. what 448 says is that after aggregating the average annual gross receipts for certain entities for the 3-taxable-year period ending with the taxable year which precedes such taxable year exceeds $25,000,000 (as adjusted) that entity or those entities must use the accrual basis. this is worthless input from a Tubotax 1040 standpoint. it's the taxpayer that needs to figure out whether their entity or group of related entities is subject to 448 and therefore must use the accrual method of accounting. there are no calculations with regard to this code section that needs to be done on your 1040.
The TT program meant to handle 90% of situations but not 100% ... some things will never be handled by any DIY program and will either need a professional program or manual overrides in the FORMS mode of the downloaded version.
From a cost effectiveness point of view (since TT is a for profit public company) there are some things the program will never handle since they are so uncommon it doesn't make fiscal sense to dedicate staff to those forms and/or they are too difficult to integrate. Even my professional program will not handle some unusual situations and manual entries must be calculated and entered on the forms directly.