Periodic transactions and time don't mix.

gistfile1.txt

7177. « ledger-test % ledger -b 2019-01-01 -e 2019-01-07 -f thing.ledger bal Ice
               1.17h  Ice
7178. « ledger-test % ledger --budget -b 2019-01-01 -e 2019-01-07 -f thing.ledger bal Ice
               1.17h
              -30.0m  Ice
7179. « ledger-test % ledger -b 2019-01-01 -e 2019-01-07 -f thing.ledger bal Fire
                 $10  Fire
7180. « ledger-test % ledger --budget -b 2019-01-01 -e 2019-01-07 -f thing.ledger bal Fire
                $-90  Fire
                
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Commentary:
so it looks like the m inside a budget transaction is not a minute, 
but the m in a normal transaction is and will add and subtract with minutes created by timelog entries.

...but, replace "40m" in line 14 with "10m" and suddenly they add again:

7188. « ledger-test % ledger --budget -b 2019-01-01 -e 2019-01-07 -f thing.ledger bal Ice
               10.0m  Ice
               
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Ledger version 3.1.1-20160111

thing.ledger

commodity m
commodity h
commodity $
account Used
account Ice
account Fire

C 1h = 60m

i 2019-01-01 00:00:00 Ice  Transaction 1
O 2019-01-01 00:30:00

2019-01-02 * Transaction 2
    Ice                                                        40m
    Used

~ Weekly
    Used
    Ice                                                        30m
    Fire                                                     $100

2019-01-02 * With cash 1
    Fire                                                      $10
    Used